I do wonder how much it has to do with the new style of player they're targeting. I don't think anyone (including themselves) will try to deny that they're obviously aiming the newer games at a different audience from the first four. I also don't think it's a coincidence that the more they move towards including modes like HHM and specifically talking more about non-hardcore accessibility (ie casual-bait), the more shallow the content seems to get. SC was directly aimed at non-fans who are definitely casuals, choosing this specific type of game rather than a port or a full handheld experience of one of the full games, and look how compact and simplified that is, and how party game-oriented everything outside of story mode is. Story mode looks like it was made probably more for fans of the series, even if it is short (what with actually having unlockables and a blessed mission mode of all things), whereas the rest of the content is very much for non-committal dabbling. God knows you need to be committed to get story mode working.
5 is basically the epitome of this. It's easily the widest open game, but you're not really exploring of your own volition because of how heavily they lay the tracks and because you're basically led around by the hand in the form of the shadow-following, and when you do go off the beaten path there's virtually no reward for it. Even if you don't think they're actively discouraging exploration this way, it's hard to argue that they're encouraging it. Mission Mode, which used to be a bunch of extra content but definitely limited in terms of playerbase because of its difficulty, is gone and doesn't look likely to come back. In its place is a small number of incredibly short missions starring a character who is pretty blatantly there to stir up interest from people who are not fans of the series. The ghost list, obviously, is effectively gone, too, except for a much shorter and easier version to complete to the extent that it practically completes itself. Puzzles are virtually non-existent and only one type exists, and the same goes for sidequests. The notes are very repetitive and they go incessantly over and over the same concepts, so you don't really have a chance to miss out on any of the general framework of the story, and aside from Kururugi (which I still find weird as hell) I don't remember the story being nearly as complicated if you take it at face value (which may explain why it pretty much all falls apart once you do take a closer look).
I think a lot of this has to do with what ^ Greek said. The current style of horror game seems, at least, to be a lot more action-oriented and speedy, using things like constantly throwing enemies at you and more grotesque/visual-horror styles like all of the chopping up and blood that 5 has, even with the comments they made back in 2001 about not wanting it to be too gruesome at the risk of driving people away. Most games are more concerned with making jump scares pop up constantly in your face than actually slowing things down and taking time to build the world and atmosphere to scare you in a more subtle way. There's a big discussion in here about whether you think the atmospheric way is too slow or whether you think that constantly being pummelled by enemies causes them to quickly stop being scary due to overexposure, but that's probably for another time. From the style of 5, though, I'm pretty sure at least someone high up on the team isn't exactly a fan of the atmospheric method.
Having the game broken down into missions makes it more bitesize and easier to jump in and out of, too, which seems geared towards people who don't tend to play it for extended periods of time or just as a quick and spooky time-killer, rather than the old style which flows continuously even between chapters. It's less of a commitment and more digestible, especially now that everything has its own little plot summary right there as you go. It seems designed more to cater to people who do play in short-ish bursts, which I'm pretty sure most of us don't if we have the option, and that may explain why it's so frenetic - to keep these people interested. If you play a lot in one sitting it feels like a chore after a while with how much fighting you have to do, but they were probably afraid of the short burst players stumbling upon a more slowly-paced chapter and getting bored. In the very first chapter you meet Ouse, in the second you essentially have a mini-boss... it's pretty unrelenting, and the slow build seems to have been sacrificed for it. Ghost hands may have slowed the game down quite significantly, but they also act as an artificial tension booster, so even something as mundane as picking up an item means that you're constantly under fire and something is always being thrown at you.
So, what does all of that rambling have to do with easter eggs?
Perhaps, casual player doesn't want to think, see 'Game Over' screen or to explore his ingame surrondings while he is playing (and he has to if he wants to find easter eggs), the only thing that really matters is actually 'press x to win' and be done with this game so you can move to the next one.
Pretty much this is what I'm getting at, yeah. They've very clearly adopted a more linear style at this point. They're aiming for a less hardcore audience these days, and they don't expect them to do very much exploring or hard thinking about things like puzzles, hence why that's been almost totally stripped out. If you're expecting your players to pretty much let the game play itself without taking much or any time to look around, there's very little point spending time putting in breadcrumbs for them to (not) find. Easter eggs only work if you find them, after all. Everything is basically presented straight to you to guarantee that you see it, which might explain the encounter rate being out of this world. Could you imagine them hiding something as carefully as Stroller Grandma's ghost now when it took so many years for even a more hardcore-oriented playerbase to find it (and not without tricks even then)? There would be no point.
Whether you think there's been an influx of casuals or not, they make no secret of the fact that this is who they want and expect to be playing. They're going to do things they think this kind of player wants to see. Aside from not sticking around to finish the game if they deem it too hard or slow-paced or whatever, they're probably not very likely to play the post-game content, which is why we got Ayane and why the number of unlockables seems to be practically halving with each new game. I think mission ranks and things like the lens that lets you hear their thoughts might have been put in for the people who actually do stick around, but they only make up a tiny portion of the game and still aren't particularly deep. Sidequests require you to wander around and find things for yourself, which is something that 5 especially seems to bend over backwards to stop people from doing, not to mention that they make the story deeper (which the ghost list shows they're clearly not interested in doing), and god forbid might even require you to do things over multiple chapters and thus make them less segregated and episodic, which also makes jumping in and out harder.
To (finally) end, then, I'm pretty sure it's a combination of them viewing easter eggs (and bonus content outside of the main story in general) as pointless given that the audience they want to play the games will probably never find them or give a damn about them if they do, but also them being afraid that the old style of hiding things and building the atmosphere in a more subtle way would make the pacing turn people away, hence the increasingly action-oriented style and apparent attempts to make it even more action-y. Fast-moving gameplay and a constant conveyor belt of instant gratification in the form of in-your-face scares doesn't leave much room. Not many people they're trying to sell the game to want to sit around watching an LP of someone meticulously combing the game map for notes; they want to see screaming and big reactions, like those night cam videos of people shrieking at a screen that are such a popular marketing tactic in this genre. Easter eggs and little wink-nudges don't fit into that, since they're for people who do enjoy getting deeper into a game and therefore are in direct opposition with the people they're targeting, so unless the marketing strategy changes considerably we can probably kiss goodbye to them.
Replay value is gone because you're not expected to replay it. Instant gratification and gimmicks up to the eyeballs is the new way. As much as I miss the days of things like dust pictures in mirrors and bloody hands showing in innocent photos, those unfortunately don't market themselves in the way that mutilated ghosts, gimmicky control schemes and seethrough shirts do. In their hurry to constantly shove things in people's faces, they seem to have forgotten how effective a shadow in a window can be.