They would consider it an insult to call them social clubs, but to some extent that is what they are. If they are functioning properly they will try to appeal to certain subsets of students so that they can form a cohesive group. They spend a lot of time together, learn the ropes of how to manage an organization, have opportunities to have social functions with members of the opposite sex, some of whom presumably are potentially marriageable mates. They are lot of fun and have a lot of parties. They are also a commitment.