And aside from the insurance part, the AMA has done so much to help the hobby grow. Without it, aeromodeling would still be mostly C/L or maybe simple RC planes being flown in parks and school soccer fields. The whole notion of an RC club with it's own permanent facility took the leadership of a national organization to take root.
It's like people who go to church but maybe complain about some of the procedures or policies of the denomination. But without the leadership, that church probably would never have been planted to begin with.