I've actually never had anyone leave on me, but then again, the one time (maybe two?) I've won, it was a sneak attack because I am ninjaninja
Lol. But I actually never initiate Tic-Tac-Toe because it's still a bit buggy for me. I also have an ancient computer that dates back to when dinosaurs roamed the earth, so things tend not to work very well for me, regardless lol.
I haven't had anyone quit on me yet and I've won quite a few times.
It usually depends on who goes first.
It's kinda silly to leave though, it doesn't count against you in any
way so what's the point? It's just a game, take the hit.