Anyone who's played above an open level in this thread seems to think that teams in open should be happy at the level of competition and should stop whining, but what you don't seem to understand is that teams in open are more than just goofy names with new aliases; they're human. And, more than likely, they're new to competitive tf2/competitive video games, so when they go 3-13 in the season, it's not going to inspire them to keep playing, and in most cases just creates more opportunities for the team to cave in due to internal drama.
Now I'm not saying that people are incapable of handling losing matches are just games in general, but a good part of the reason why the divisions exist in ESEA are to maximize the possibility of teams being close to equal in terms of skill, as well as keeping the game fun for everyone. Personally I've dealt with people who lose a match and curse out teammates/rage in mumble/be extremely unproductive; I've also seen a lot of people lose and come off as not being affected by it emotionally at all. However, when the concept of divisions works effectively like it's supposed to, a good majority of players are given more of a chance to develop themselves at the base skill level, while minimizing the chances of them having the game ruined for them.
/rant