It's a lot of things. Right now the behavior itself is self-perpetuating because there's no reason for players to change.
Some of the factors I see as impacting MA play include:
- The game rewards individual kill streaks, regardless of how they're obtained. The brag messages in this case. Easiest way to get a "wtg" is to vultch a field - so why work any harder? For "gamers" this makes a difference. At the same time, gamers also like squads/clans and this should become more of a focus.
- The mechanics of field capture turn the activity into either a vultch opportunity, a GV-killing snooze-fest, or an unopposed steamroller. There've been lots of suggestions on how to change this. You'll always need numbers to win, but right now the numbers don't need to be terribly well organized or skillful - so no one really improves or learns a damn thing.
- Many, many little imbalances and quirks which people play "down" to because it's easier. Shooting down CV's and CA's with cannons, heavy bomber formations at 500 feet, GV's of all types which at times are all but immune to attack from the air, HO's are just too easy as are long range shots beyond 400 yds, too many pork-n-auger opportunities which keep many freelancers in the role of nuisances who die after their 2nd pass on the base.
- Not enough change. This is a huge thing which is tough for HTC to cope with because they are a small company. But history has shown that player numbers increase and idiotic stuff declines when there's something new added to the game. New planes, new capture rules, new features, etc. - new maps don't count because the game itself doesn't change and the maps are all so tightly packed anyway. If the game stands still, players will find and use the easiest paths to "success" - and that path is as often as not harmful to overall gameplay. (Those old enough can recall the old "radar runners" from AW which just made the arena a total bore.)
So, again, it's a lot of little things that don't change. The good thing is they're easy to fix - even if only one at a time.