I think the assumption has always been that panfish will take most trout flies and bass aren't that picky so a large variety is not necessary for them. Both those suppositions are basically true, but not in every specific case. The industry is starting to realize the potential of the warmwater market (the other assumption was that most people who fly fish do it for trout) however, and are bringing out a larger variety of warmwater flies, especially for bass and carp, every year as they become more publicized and popular targets for flyfishers.
If it swims and eats, it'll eat a fly.