Research shows people flirt with one of no fewer than six different reasons. Some people still are looking for a mate, of course. But we also like to flirt because we enjoy it. This kind of flirting "is kind of like racquetball," says Dave Henningsen, professor of communication at Northern Illinois University whose research and reading of the literature identified these six goals. "It's fun, and we do it together so we build our relationship."
Sometimes we want to explore what a romantic relationship with the person might be like. Or we want to reinforce or increase intimacy in a relationship we are already in. We may want to boost self-esteem—whether it's our own or the other person's. And some of us flirt to get what we want—a dark art that Dr. Henningsen refers to as "instrumental flirting."
Or, to simplify things, you could just cram each of these motivators for flirting over into the "because we enjoy it" column and call it a day. That is, as long as you "enjoy" getting what you want from hot friends, lovers, and coworkers who also think you're hot.