Windows machines need to be on for about half a day every week. I know no other device that needs this kind of attention, apart from helicopter gas turbines that are best kept slowly spinning.
Microsoft thinks just because Google can force-feed Chrome updates to users, it can do that with Windows too. It doesn't seem to comprehend that an OS has fundamentally more stringent availability and reliability requirements than a browser.
For example, my Chrome ("stable") right now just renders most new windows as completely white -- no address bar or anything else. Because Google decided to force-feed me a buggy version I never wanted or asked for. So I have to open 2-3 new windows before I get a working one. It's painful but I can still do that, or use Firefox/IE if all else fails. If this kind of crap happened with the OS I would not be able to use my laptop at all.
It's also a different install process. Chrome doesn't decide to automatically close itself to apply the updates, and they are applied fast enough that you usually don't notice unless something changed. Neither can be said for Windows - the reboots are often unexpected and the install can be lengthy. If Microsoft got it closer to Chrome (no forced reboots and applied without triggering a potential long "Configuring Windows Updates" stage), it'd be much less of an issue IMO.
For example, my Chrome ("stable") right now just renders most new windows as completely white -- no address bar or anything else. Because Google decided to force-feed me a buggy version I never wanted or asked for. So I have to open 2-3 new windows before I get a working one. It's painful but I can still do that, or use Firefox/IE if all else fails. If this kind of crap happened with the OS I would not be able to use my laptop at all.