There may be a number of reasons for joining fishing clubs including social companionship. I have been a member of a number of fishing clubs and I think the main benefit has been to go out fishing with a few mates.
Another benefit of a club is that some of the people know a tremendous amount about fishing in general and others know a lot about one specific type of fishing. Either way you can learn a lot from other people.
Believe it or not you also have a lot to offer the other members of the club and that in itself is really gratifying. Sometimes it is better to give than to receive. I know that sounds corny but I get a great thrill seeing others catch big fish for the first time in their lives.
Hope it helps mate. All the best.