RAM has it right--
People who can't actually play the game would be left out using that system (including me). While HTC has no obligations to people who don't pay for their product, believe me, it GREATLY adds to this community to allow anyone to post--especially considering the poor community support in the actual game (which is AH's only real downside). Basically, HTC saves themselves from having to expand the game interface by supplying these boards instead.
Also--just because someone doesn't pay for the game doesn't mean that they can't have a good idea or foster a good discussion. Furthermore, through the H2H feature non-paying people can still use the game, so their input definately IS valid.
AirWarrior, for example, uses the system you recommend--you have to be a subscruber to use the messageboards. While their boards have an excellent little community, VERY FEW new people ever say "hi" there and generally it's somewhat stagnant. Not necessarily a bad thing--there are VERY few "bad posts"--but decidedly different from THIS messageboard. AirWarrior's system suits them very well, I feel, because the game itself supports their community. However, that system wouldn't necessarily apply well to Aces High.
As a comparison--total posts on THIS messageboard per day: Hundreds. On AW's boards: 50-75 on average. Aces High's boards are MUCH more active.
Each system has its advantages. But be aware, there are also disadvantages.
I feel that Aces High NEEDS a widely-available messageboard, because in-game community support is decidedly lacking. I feel that, unlike AirWarrior, if Aces High limited acces to their boards it would hurt the game more than help it--at least until AH has better built-in community support.
J_A_B
Note: I also like this game enough as to want to be able to keep up on the various discussions, and make what small contributions I can to discussions.