I've had that done to me and done it to other people. In my experience, it's pretty typical to have at least a period of no contact after a romantic relationship ends. Some people I've gotten back in touch with later on.

I had one guy who stopped talking to me four years after we ended our very brief romance - I think his girlfriend put the kibosh on our occasional texts and visits, but I don't really know - I just know that it took me about six months to realize that he was really not responding on purpose

Another person stopped talking to me cold turkey, I think because he knew that if he did, I would talk him into trying again. I was not willing to let him go and he knew that -- and he knew that any contact with me would just make me hope for something more. That is often the reason I cut off contact with exes.

Sometimes it's because the temptation to get back together is too strong. Sometimes it's because one person has already started dating someone else. It could be because the pain of the break up is still too raw. Maybe one person has realized that they don't want to be friends after all.

Maybe this hurts so much because his actions demonstrate that he doesn't care about you as much as you care about him? It's like a second rejection on top of the breakup, a rejection of friendship on top of the romance.