Well.. all depends on the country.. Here "traditional yacht clubs" do take cats.. ie Nedlands Yacht Club houses the H16, Windrus and T fleets.. It housed the Bs, As and Cs years ago..
Of the clubs on the river I guess half have or do race cat fleets.. Off shore clubs again half of those in the main population are have cats.. In outer areas I suspect all have a cat open fleet.. There is also one cat only club..