I think the lack of cats is because of the few sandy beaches. Most of the mono dinghys are kept at the various yacht clubs around the bay and are launched off a hoist that swings them from their trailor to the water and drops them in, or, in the case of Lasers, they can store them on a rack and launch them off a dock. Cats are too wide to do that off most docks.

We need a solid sandy beach to roll them off the trailors, onto wheels to the water, mud won't work and rocks are death. Oh, and the water up there is cold, cats are very wet, especially when it's blowing, so wetsuits are in order even on a warm summer day. SoCal has the sandy beaches, warmer water, etc. so there are more cats there.