He may or may not have understood the concept of in-memory caches and unsaved user work, but it didn't much matter to him.
I know it's easy & popular to rag on BillG, but toward the end of his tenure at MS, he did occasionally come out as an advocate for users & pushed for simplicity & fixing broken things in their ecosystem. Take this example from when he attempted to install Windows Movie Maker in January 2003.
But back to the shutdown thing.
As a naive user, why should I have to ask my computer for permission to shut down? When I tell my TV to power off, it just does it. When I turn the ignition in my car off, the whole thing stops. Same with my VCR, my cell phone, you get the idea.
As a non-naive user, why is it that when I tell my XP laptop to Hibernate, 5% of the time it just flips out, every application crashes, and I can't do anything, including just shutting the damn thing down until I've cleared all the "this program has crashed, how would you like to debug?" messages and then wait for the UI to become responsive finally to the point where I can tell it to shut down. And then takes 5+ minutes to actually shut down. When I close the lid on my MacBook, OS X puts it to sleep. When I open the lid, it wakes up. Every time. Why can't Windows do this? I can't just go to Standby because it drains the battery too much, so I have to Hibernate.