5e's big issue with the culture surrounding its optional rules is that they make things optional that people like and expect in their baseline. Which creates this feeling that something you could somewhat take for granted before can be stolen from you at any time, which people in turn reject by applying social pressure to weld it back onto the baseline so that a culture of denying it can't take hold. Each of those stories about players being shocked, angry, and dismayed when its not available speaks to how the game's actual baseline doesn't really meet their standards very well.
On a basic level, this is a product of it being a compromise game intended to be played in such dramatically different ways-- some of the people you're sitting to play with have very different assumptions about how the game should work than you do, its not really about standardization at that point, its about whether the players get to play in a game they enjoy, or whether the GM gets to run a system they enjoy. It creates scenarios that for players, no matter how irrational this sounds, feel tantamount to advertising a 5e game and busting out ye olde Rules Cyclopedia instead when everyone sits down to play-- you and they are expecting fundamentally different experiences and neither of you is actually wrong (although we could make a good case that the players should be more open minded, or that the GM should consider working the optional stuff in since the players want it anyway.)
The other issue, is that it lets the system get off with being 'buyer-beware' about every optional system it produces, which is a problem since those systems are often the ones most in need of system integration and balance attention. This creates situations where the GM is antsy about allowing/using them for the integrity of the game experience, but the players are antsy about not using them, because that deprives them of tools. This includes magic items too, if you aren't being sparing with magic items, or banning feats like GWM in concert with +2/+3 weapons, the game takes no responsibility for the resulting messes.