Mary,
From where I come from running a saiing club is a very costly business. We not only pay for insurance, initial purchase and upkeep of rescue boats and safety equipment. Radio Licence, Council rates, Rates to the Dept of Land and Water, Aquatic License so we can set a course on the lake, AYF fees, upkeep of club house and things like annual Fire insoection certificate the list goes on and on. It costs over $10,000 per year to keep the club going.
In the course of a finaicial year, if we are lucky we just break even. Without the income from running regattas and State and National class title events we would not survive.
There are many different reasons why people go to regattas and there would be many different reasons for different clubs, depending on their individual circumstances, for running regatts. Most of the clubs I know of run them to survive.

Regards,
Phill