Because variety and balance cannot be achieved without artificial intervention. The whole "natural equilibrium" concept is bullshi*. It has always been.
Ofcourse, that'll probably lead to the discussions on whether if we really need "variety" and "balance" at all...
Which in that aspect, AH does not need to grow any further anymore. Because anything that will not see use, is a mere waste of time and money for HTC.
So, if we want merit for more planes and more features, and if you want to shoot down more different planes in many different types of battle conditions(which, I probably think has to do a lot with what people call "the fun factor"), we need variety and balance.
Ofcourse, some people may not be bothered by fighting the same handful types of planes over and over and over and over again - their concept of fun lies with pure contest of ACM, or that's what they say at least.
Which is kinda puzzling since they don't seem to like an idea of a air combat sim with just one or two planes modelled, but investing all the rest of the development time into developing realistic features and eye-candy. Apparently, according to their logic, it won't matter if they had only one plane, as long as they have someone to fight.
But of course, in reality, people won't pay to fly an online game with one plane. So I guess the basic fundamentals for "fun" is pretty much set - lot of different planes to enjoy.
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So then, how will they enjoy those different planes when certain conditions of the game promote the use of only certain aircraft types?
Yup, nobody forces them to use the "big four", but it's just a conclusion they reached on their own - they like fun in variety, but they also like the fun in killing stuff.
They grow tired in fascinations to other wonderful different plane types when they get repeatedly shot down by the fastest and turniest of them all. In the fastest, you may not win, but at least you won't lose much. In the turniest, at least you get to kill one, before getting killed(but if it's too turny and too slow at the same time, they won't get a killing chance, so naturally they flock to the next turniest, but also averagely fast planes..).
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So basically that's the logic behind limiting choices. There can be a natural method of limiting overuse - via changing the very fundamental aspects of the MA so people naturally achieve variety, or artificially limiting choices through perks.
The first method is preferred, and it is the most idealistic of all solutions but it takes time and money, and besides, the power's not in our hands to do so. We don't have the power to force the second method, but it provides easy temporary solution which can be experimented and fine tuned, so it provides comfort and satisfaction until the developers can really tune the more important issues.
