Airplane access is a persistent problem in aviation. Sure, you can rent from a flight school, but daily minimums and availability are a drag. Flying clubs provide better access, often for less money.
The last time you were part of a club it probably involved singing or playing chess in high school. In a lot of ways, flying clubs are very similar. Most have a strong social element that bring together people with a like interest. All offer a quasi-ownership model that usually leads to relatively limitless airplane access, cheaper rates, and often higher performance airplanes.
Clubs can be such a strong driver of a positive experience in aviation, that many airplane owners are also club members, simply for the joy of spending time with other pilots, and the opportunity to fly different airplanes.