Just another example of the long-term trend toward homogenizing everything to work under the same core mechanics with only the labels varying.
Well, that's because any time the game has tried to introduce "new things" that aren't a part of the core gameplay, barely anyone incorporates it or uses it. You might get the miniscule amount of diehards that think its the greatest thing since sliced bread... but 99.99% of the rest of the playerbase never even bother looking at it, and thus when the edition changes there is almost not a single call to reintroduce it into the new game.
See: True names, Incarnum, Residuum, the countless attempts at mass combat, bastions and other stronghold rules, epic levels, and indeed psionics as a part of core gameplay.
Sure, some people are pissed that none of this stuff has ever really caught on with the main thrust of the D&D playerbase... but you can't blame WotC for tossing that stuff overboard. They tried it once... no one cared... they didn't bother to try again. Especially considering that if there actually WAS a market for any of this stuff... we would have the 3PP and DMs Guild designer crowd out there picking up the ball that was dropped and producing the material that those players wanted for all these things. But guess what? Most of it
still doesn't get made even by outside companies/people, because there's genuinely no market for it.
And for the few things that DO have a possible market? Like Psionics? Well, in that case it
doesn't matter what the 3PPs produce because most of the players
still refuse to use any of it and instead sit on their hands caterwauling that WotC isn't making it themselves. And... even when WotC possibly
does make it, the players then complain about what WotC comes up with because it isn't the psionics they want. Quite frankly I think WotC shouldn't even bother trying to placate those players ever again because those players are never going to be happy no matter what WotC OR the third-party producers make. And if that means they are no longer "under the big umbrella" of D&D? Well, too bad for them. That's their choice by having demands so far out away from the WotC umbrella that it's a waste of WotC's time and money trying to chase after them. There are plenty of other games to play and no one is going to be mad or quite frankly care if they wander off to go play them and leave D&D behind. WotC certainly won't.
