I've been thinking about this a little more and reading some of the comments I feel that there are a number of differing (geographical) reasons we all feel so different.

1, The French as someone said, try to bread 420 -> 470 crews etc...
2, In the UK cat sailing is VERY much the poorer brother to mono sailing. At my club(the biggest inland club in the country), the cat fleet is (probably) about 5% of the whole club. A vast number of clubs around the country do not allow cats to sail on their water. within the UK, I would guess (and it is just a guess) less than 1% of people sail cats. If we loose a youth sailor to the 29er which does feed into the 49er, they won't come back to the F18 and Tornado. There are a lot of people who have worked VERY hard to encourage our kids to sail cats, but then these kids get forced to sail H16 (well they don't because they won't sail them and move to the 29er as my comments above).
3, From what I can gather there are many more cat sailors in the USA and Aus. and so the UK situation is unique (we have to try and keep the talent, and the Hobie 16 is not helping)

Just my observations on what has been said.