The real question is, after 30 years of personal computers, why can't we simply hit the "off" switch or pull the power plug?
On my Windows boxes, the (soft) power switch works just fine, thanks. It's set up to do a graceful shutdown, so it won't shut down if an application foolishly needs to ask me whether or not to save changes, but that's mostly the application's fault (see Notepad++ for how to do it right), and I could set up the power button to do a "maintenance shutdown," which force closes everything, if applications were written better.
Powering off without any notice at all, safely, would really limit performance in many ways - I'm just as happy to wait a second or two for unsaved changes to be parked, all the write caches to flush and so on.
I want a computer that I can just switch off, then switch on and be instantly back at what I was working on, or at a login screen. Instantly.
Basic physics will keep persistent storage slower than volatile memory, but if you're content with 1990s performance, you could probably build a PC that worked that way. Heck, it probably exists for some exotic use case.