Class proliferation...

Personally, I really dislike yardstick racing because all too often it gets down to the conditions suiting the boat rather than the sailing, but that's just personal. 

One interesting thing, though, is that it seems to be a UK cultural issue. The other countries that are arguably in the "big three" centreboarder nations, Germany and Australia, seem to be very much into class racing at clubs. In Oz I feel that the places and disciplines that have maintained a class racing culture have done better at retaining numbers than those that haven't maintained that culture, although that may be a result as well as a cause of declining numbers.

Arguably the UK preference for yardstick racing is perfectly understandable (although the sport boomed when it was almost all about class racing) but it doesn't seem to be universal or a product of technological or societal changes per se.

You are, of course, dead right when you say there were many more classes in earlier eras. I'm looking at a 1962 YA Yearbook that includes classes like the Swan OD, Haven OD, Stormalong, Clipper, Delta, Mayflower OD, Brandy Hole OD, etc. But the other thing that strikes me is that while there were many tiny classes, the major classes seem to have been enormous. On the second weekend of the season, for example, the Ents had three different interclubs. On the next weekend, there were four of them. On the last weekend in May there were Enterprise interclubs at Exmouth, Poole, Gresford, Wraysbury, Loch Earn, Felixstowe Ferry, Colemere, Littlehampton, Hornsea SC, Horning SC, Peterborough, Putney and Avon SC. That same weekend there were no fewer than 11 Firefly interclubs. 

That was a huge amount of class racing, even without counting the clubs. The Ent was a "regularly raced" class at over 100 clubs - and that's only at clubs that start with a letter from "A" to "L" because I got bored counting. It does seem logical that the accent on class racing would have helped the sailing boom. Certainly that seems to me to be explicit or implicit in the writing of people like Beecher Moore and the creators of classes like the Snipe, Opti, Windsurfer, Hobie etc.

One amazing stat is that in 1961, there were 58 new clubs launched and 2,500 new personal YA members - and both those numbers were just par for the course in the post war era.