Most clubs REQUIRE AMA membership.

They do so because of liability issues. AMA sanctioned clubs enjoy a degree of insurance and protection given by the AMA itself.

AMA members also get liability insurance as part of the membership. This insurance DOES NOT replace your home/apartment owner's insurance in case you do something, you plane hits somone/something, etc... but it does provide additional coverage over what you should already have.

In addition you get the magazine, and the AMA is quite active at doing things to help support the hobby, such as the recent FAA bill lobbying in congress.

You can often visit and fly as a guest at other clubs with nothing more than your AMA card and proof of certification/membership at your home club.