My yacht club has a diverse membership. While most of the members live and boat near the club, there are several who rarely visit the club and keep their boats in another harbor. We even have a bunch of members who have joined for the social aspects.
The big advantage of a club is the depth of knowledge about sailing and boating that the members possess. When you need hand with something, there is usually someone around who is willing to lend a hand. Club members will often watch out for member's boats during storms or just in general. If a member sees something amiss with your boat, they will either contact you or take care of it for you.
If you want to race, then club membership is essential as most clubs won't allow nonmembers to compete in their local racing.
If you cruise, in most regions clubs offer reciprocal privileges. You can visit another club and stay at their docks and use their facilities for no charge.
Yacht club bars are often less expensive than local bars.
All volunteer clubs often have a requirement or expectation that you volunteer for work parties, regattas, or committees. It is important for the club's functioning and for meeting other sailors.
For me, the biggest advantage is the knowledge base of the club members.