Because, the snapshots and events, which no doubt is the cream of the crop on the potentials what people can do with AH, is still limited - it is largely player organized and driven. A voluntary spirit(and no doubt, very powerful one up to date!), is the only thing which keeps it going.
For various reasons, many people don't have access to regular participations in events and snapshots, Tours of Duty and etc.
The majority of newbie players are inevitably discouraged by the organized concept(while they certainly should not be, still, people can't help feeling that way - it's a natural thing) of events and snapshots, and Asian/Aussie/Kiwi players in the far east can hardly participate - unless they are devoted enough to get up at 3AM in the morning. (There has been attempts for Pacific time zone events, but variety of reasons make it fairly impossible - unlike US/Europe time zones, about 30% of AH population in the Pac time zones are Asians, and they all speak different languages - English is seldom their first language. The numbers are much smaller than US/Europe prime time, too)
Thus, in many cases, for many paying users the single AH content where they can regularly log on and enjoy the game, without complications, is the MA. Besides, seeing a plane which HTC has worked hard to model and implement within the game, used only in a handful of events per month, can be considered a waste of resources.
For such reasons, inevitably, the analysis sets its grounds upon the MA - because, it is the only common factor which AH players share all over the world.
It is where the largest number of people hang out, and it is the main material which makes AH an MMOG.
