I'm an avid tennis player. The parallels between the tennis world and waterskiing are interesting. Millions of people play tennis at all levels as a recreational sport. These folks don't need to join a society to play a friendly game. However, if you want to compete, you must be a USTA member. They have a hold on that aspect of the sport and are responsible for rankings, etc...
How many folks out there like to ski with a recreational intention only? Take the family out on the boat and free ski while enjoying the water. This is probably the vast majority of skiers. We don't all want to compete. No need for those folks to join and support USAWS.
At the end of the day, these governing bodies and our "elite" athletes are the ambasadors for our sports. The do need to step up and encourage participation at a grass roots level.