I'm in the beta program for macOS Sierra and the last 2 updates have tried rebooting my computer without any warning whatsoever. The only thing that "saved" me was having iTerm up and running and it won't close with active terminals open. In the past, OS X was really good about asking for permission to update. Now it just assumes that I'm ready whenever it is. Maybe there is a setting to turn that behaviour off, if so I don't know what it is and it's really starting to make me doubt Apple's commitment to professional tools in a whole other fashion.

This is true of macOS as well now. You can defer it, but you're nagged pretty consistently. There was a time I remember when installing updates on OS X didn't require a reboot unless it an os update. Now, so many things are tied together.

This doesn't require a system reboot, but if you're updating Xcode, you can't if iTunes is open. I understand shared libs and things, but I don't really see that much difference anymore between rebooting for Windows updates and macOS updates. YMMV I guess.

IIRC if you pay for the "Pro" version of Windows, you can defer updates.