I'm at the worlds at the moment and with only a 100 boats, participation really is quite low.
I think one of the reasons the number of entries is down is the reputation of lake Balaton as a low wind location with the typical lake winds.
Although I dont know how on earth you could fit 200 cats here anyway, there is barely enough room for a 100!
Another reason is the distance, its a 1400km drive which is a lot for european standards but its not too bad as the roads are really good.
IMO the Argentinian team did the smart thing by renting a Nacra in Holland for a few week, they did the Nacra Worlds, Round Texel, and now the F18 Worlds.

Winds were very shifty today, spent 5h on the water but every race was abandoned due to huge shifts and differences in pressure.
In one race you could do the upwind tack with the kite up!