It's a way to flirt. Teasing communicates effectively: * I'm not a threat to you, being around me is safe. * I have humour * I am fun to be around As the o

It's a way to flirt. Teasing communicates effectively: * I'm not a threat to you, being around me is safe. * I have humour * I am fun to be around As the other commenter said, it creates bonding. You only tease people you like. I can't think of a faster way to demonstrate these qualities, which are perceived as very attractive.