It makes sense to listen to gossip in order to keep track of what folks are up to. But it seems the main reason we listen to gossip is to prepare to speak gossip, in jockeying for status:

We have consistently found that people are most interested in gossip about individuals of the same sex as themselves who happen to be around their own age. We have also found that information that is socially useful is always of greatest interest to us: we like to know about the scandals and misfortunes of our rivals and of high-status people because this information might be valuable in social competition. Positive information about such people tends to be uninteresting to us. Finding out that someone already higher in status than ourselves has just acquired something that puts that person even further ahead of us does not supply us with ammunition that we can use to gain ground on him. Conversely, positive information about our friends and relatives is very interesting and likely to be used to our advantage whenever possible.

For example, in studies that my colleagues and I published in 2002 and in 2007 in the Journal of Applied Social Psychology, we consistently found that college students were not much interested in hearing about academic awards or a large inheritance if it involved one of their professors and that they were also not very interested in passing that news along to others. Yet the same information about their friends or romantic partners was rated as being quite interesting and likely to be spread around.