The National association in any country does a lot more than just supply insurance,and I dont agree its the main reason for existance.
For Canadians reading this thread ,be aware the situation in the US is much different than in Canada,since medicine is nationalized here and personal injury claims rare as a result.
The claims experience in Canada is very low on the MAAC policy and have been of the "model lost control on takeoff and hit a car" variety in the last couple of years.It is arguable whether good safety practices or dumb luck has kept us out of serious trouble so far.One high loss permanent disabilty or God forbid death claim can easily run into $millions these days in a hurry.
Initial indications for future costs of liability insurance for anything involving the word "aircraft" are shocking currently,thanks to 9-11 and U.B.L.