Why do we have so many regattas..??

That is easy... there is no catamaran fleet captain who has the authority to tell a club or organization... Sorry we are not coming this year.... No one speaks for Open class... the One design classes may pick some events... but the rest of the races are essentially open class events for those fleets.

Equally important.
From the clubs point of view... adding your class is trivial. They just order some more generic trophies.. (use em next year for a different class) Any extra boats makes the regatta financially successful. Bottom line there is no incentive to cancel a class start.

We just got suckered into a monohull start with one other boat... The Yacht club has no worries... they made money. We wasted our time. The owner was not happy! especially when the race time limited out.

as Ding would say... It was One Design!!! did not make an impact on the owner.