Why do some people enjoy playing with others' emotions?

For some its fun to play with others emotions. And whether it’s malicious or not, it tolls you.

I’ve had this happen to me with a guy. He would lead emotions on, like he would invite me over, but then never answer back when I’d accept. I heard from his friend that he “leads emotions on”.

But I’m curious of the actual reason. What can a human possibly gain in doing this? It would be a waste of my energy and voice to be honest.