I’d be curious to know what the default mode is. I couldn’t really find it online and it looks like games can override the console settings anyway.
If performance mode is the default then I’d imagine people just can’t be bothered to change it. If it’s not the default then I’d imagine people changed it to performance mode cause one game ran poorly and then couldn’t be bothered to change it again. People just want to play most of the time. Not dig through menus.