I think its because for the guy screaming into the enemy base, he has a choice...lose your E by manuvering to get shots on those around the base, and opening yourself up to aa, or scream in and killing the easiest target, the guy sitting on the runway.
I think it happens on all sides, and I myself have done it often when I real fast..too fast to get shots on anything else.
That said..it is the MA where anything and everything happens. If WW2OL taught me anything, its that you can't create a game, and open it to players from around the world and expect everyone to play the same way, or the way one person, or the designers envisioned.