Mark, here in Australia, there is a place for both competitions. The F18 has developed into a pretty high-level contest at local and national level with the best sailors from all classes having a go. There are also plenty of Tiger sailors who want to class race and join in the fun at a Hobie Nationals without the intensity of F18 with its measurement etc,etc. A Tiger class sailor gets a few seasons out of a set of sails.
The keen guys do both, some choose one or the other.
F18 in Australia was originally formed by the major classes to be an additional parrallel competition. Nacra and Capricorn also hold class Nationals.
Maybe we just sail more than the average USA sailor.
A keen racer here can compete in competitive regattas within 10 hrs drive a couple of times per month. Some guys do just that.