Gamers: Wants more and moar demanding visual eye candy.
Devs: Sure, we can do all that, we just need time to implement it all, and for playtesting.
Publisher: Doesn't give them the time, and probably not enough playtesters.
*game launches
Gamers: WTH, why does this run so poorly, etc...
Devs: Rush to put out a patch, because they weren't given enough time, and probably playtesters.
Publisher: monotone "We're sorry..." [Think of that one South Park episode]
This can't all be blamed on 'lazy devs' every time things go wrong. The more they need to add in, the more time they need. Plus, console has the same specs; just plain easier for them to work their magic.
The publisher is only going to wait so long, and - UGH, AAA games are more about the shareholders now. Not that they weren't before, but it's definitely worse than it used to be.
The consoles' unified memory is faster and more efficient than the PC's outdated separate one. So with 'all the bells and whistles' enabled on PC's slower throughput, more vram will be used to compensate.
Hmm... maybe that's one of the reasons Nvidia wanted their own cpus(ARM)? Nah, couldn't be...