Any form of entertainment has its problems. If you demand more expertise at a dance than someone knows, then they won't be back. If you keep the program too simple, then some people will get bored and leave or invent their own entertainment by adding their own special moves to the dance. It is all part of who we are and what we enjoy or don't enjoy. Maybe the answer is to quit wishing everyone would fit into the same mold.
Most people have limitations on how much they can or wish to learn about dancing.
When they have either satisfied their interest in learning or reached their limitations in dancing ability then other factors take over. Many of these people can be retained in a recreation by the careful cultivation of other reasons to stay within the group. A very strong factor in retaining dancers over a long period of time depends on the friendships that are made within any group of dancers and the support these friends give each other. People will continue to attend dances if they feel they have the support of friends. The promotion of friendships among dancers should be an active part of every set of lessons and every dance a club conducts.