The 9-3 Curse: the phenomenon where the team who is up 9-3 at the half, will eventually lose in the end.

What I mean in the title is that when people get 9-3, people start getting really caught up in that score line, thinking the curse will happen, and a lot of the time, it does happen. But is it only because that score is popularized with that connotation that the upsets happen in the first place?