Perhaps I missed it, but where is it stated in the AMA's mission statement that the AMA's role is to provide convenient low cost flying sites to members? Better yet, where is is stated on their 501(c)(3) application as a a purpose of their organization?

Fair enough, but I contend that if nobody is flying because they can't get easy access to flying sites, doesn't that eliminate any possible need to be a member of the AMA?

The AMA has already incentivized model aircraft activities by offering clubs the ability to get insurance coverage for land owners for flying sites.

Again, but if they're too far away or too expensive, will more people use them? Or fewer? If the latter, at what point will they collapse under the economics? On the other hand, if you can fly within walking distance, and are happy living with the limitations due to size and type, again, no need for AMA membership to enjoy the hobby.