What do you use actually that doesn't have "undo"? I can "undo" the whole day of my work on the file until I close it in the IDE. Whatever is "lost" I can return to the previous point.

If you're asking why I use git at all, my IDE crashes often enough that I don't want it to be my sole store of history; also I want that history available to my colleagues or my future self, weeks or months from now.

It's the way I'm used to working, I can't say how common it is. Put it this way: I want to control when it compiles, and I want it to be very obvious if the error markers aren't up to date. So the setup I currently have is eclipse with automatic compilation but manual saving; the possible states are saved and up to date, unsaved (obvious from stars in the title bar) or still compiling just after a save (obvious from progress in the status bar). When I tried to use IntelliJ with its autosaving I found I was pushing code to master that didn't even compile, because I would make a change and then not realize that this had broken something.