When you install or update something that breaks something, like has happened to me many times, to the point that the system cannot boot, you can pick a snapshot from the grub menu from before those changes occurred, allowing you to recover your system to a working state without the use of a live boot usb.

It's also been useful when some program or other stops working due to some change in a dependency somewhere, like OBS sometimes does. Then you can just hop backwards in time to a point where it works and get to actually using your system, instead of spending hours tracking down exactly where an error is occurring right then and there. "fixing it later" becomes a valid way of dealing with problems with your system, when just pressing a button lets you make it temporarily go away.