Games often bind skills or other game mechanics to the function keys.
Anecdotally, I switched from `ctrl+shift+i` to F12 for opening the web inspector due to many websites capturing that keybinding for their own purpose (claude and code editors) if I didn't have a function row I'd have to find an even more arcane hotkey.
They're just a nice set of purpose-undefined keys that you or the application can bind to useful functions.
I've played a lot of games and other than quick save, can't think of any that have used the F-row.
Minecraft uses several. Different cameras, the console, etc.
MMORPGs and games that have many different mechanics might be more prone to it, versus first-person controlled games? In my experience its pretty common.
Most likely, I haven't played many MMOs. Having to go from WASD to the function row is pretty clumsy for me, especially when there's ~20 extra keys around WASD without having to move a hand.
Pretty much required in Eve Online.