I confess to having my own theory about why that's the case -- mostly, I think the Decepticon players are outnumbered at least 2:1, if not 3:1. It's rare to see the Decepticon side of a mission get many characters, while the Autobot side routinely seems to fill up rather quickly. Probably doesn't help when the low-level Decepticon players run into "level 3" and "level 4" Autobots that should easily be at least level 5, if not level 6, by their XP alone, but won't update except to get the most killing power within that lower-level range... and I know of at least 2-3 Autobot players who have made their career off doing exactly that.
It can be frustrating, especially when you know that there's such an imbalance there to begin with, for Decepticon players to put in characters when they're pretty well assured that they'll get very little for their trouble except a stasis-lock repair bill to eat away at the energon, and if they're lucky, maybe a teensy bit of XP. The RNG gods don't seem to like me much, though, because most times in that situation I get no XP at all and lose energon for trying to help out the Decepticon side... and I've already past the point of not bothering in some missions at all because of the sheer imbalance.