It's a weird thing, but my dad (who is right-handed) uses his mouse on the left side. He says it's way more comfortable for him haing his right hand free for the keyboard. But he doesn't swap the buttons.
It was an awkward thing years ago when we only had one PC and I was living with my parents - no idea if Windows still does that, but at the change user screen it would keep the mouse settings. So between my parents and me it was a constant moving the mouse around and trying to click on the user icon and having the wrong key.







