The consequence of hurt

I've never understood why hurting people hurt other people. It seems to me as though those people know what's it's like to be on the receiving end of hurt. But the older I get the more I realize people fall into a cycle of hurt. They feel like oh well...it happened to me...so it's fair game that I inflict that same pain upon someone else. The most ridiculous crap I've ever heard of. It's dumb and makes no sense!!! Do better to get better period!