There are two, very simple reasons as to why it seems like our DBs lose out on jump balls more than other teams:
1) we remember the mistakes, bad plays, etc. our team makes more so than those of another team, and
2) it does happen more often.
The first reason is obvious and self-explanatory. The second reason is a bit more complicated.
Our DBs are involved in more 50/50 balls - especially down-field - than are those of most other teams, in part due to the fact that our DBs don't get badly beaten on routes very often. This, in and of itself, means that some passes that would hit wide-open receivers against other teams end up being 50/50 balls against us. Another part is that our opponents are more likely to desperately, intentionally throw up 50/50 balls to try to make something happen against our defense. Making 50/50 balls a part of your game-plan is an act of desperation; you're willing to take a 25%-50% risk of a turnover for the chance of a making a big play. You know going in that our defense is going to force you into a lot of bad plays. On the other hand, one big play for every two bad plays equals first downs all the way down the field - just like two bad shots plus one great shot, on the golf course, can leave you in a position to make par.
So, most teams try to throw more 50/50 balls against us because they know they must; they aren't going to be able to methodically drive the ball on us enough to win.
We, on the other hand, rarely if ever make 50/50 balls a part of our game-plan because we know that we don't need to do that to win.