Just because funniness is correlative doesn't mean its not causal. Sometimes jokes can open someone up to another, and keep them interested. Just like any other social interaction.

Why wouldn't humor cause you to want to be close to someone? Also people laugh become something is funny. Maybe the mechanism of laughter signals trust or shared understanding that facilitates group bond, which means it causitive

Funniness is certainly correlative, but it's because it comes with confidence. And confidence is really what's attractive. It's not because people fake laughter.