Bombers are rewarded for landing, just like fighters are:
- Landing message (will get you similar attention to fighters if you land a lot of kills)
- Twice the score points
- Perks
Fighter pilots and vehicle drivers have been bailing for various reasons, too (including to deny a kill to their enemy)
Also, I remember quite well how bombers' bailing got considerably less with the increase of the proxy kill range to match the icon range (before some guys would wait for type identification by icon before their bailing decision was made)