Why Does It Bother Guys When Their Exs Won't Talk To Them?

A guy I broke up with a few months ago always likes to remain friends with his exs and usually hates for a girl to hate him. I am the FIRST ex-girlfriend to ever refuse to speak to him. I didn't even break up with him via talking. Since our break-up he has tried to contact me once by Facebook IM and another time by Facebook message (none of which was endearing, mostly him being dirty to me in a round about way, trying to mask the fact that he was making it sound like all my fault that we didn't work out) but I have not answered him and he deleted me. I have bothered him more than any other girl he has dated and it is so obvious (he even checked me out in front of his new gf the other night - head turning and all). Why can't he stand the fact that I won't have anything to do with him, let alone look his direction? It's like it eats him alive.