Why is Alan Rickman unmarried?

He isn't married because as a world famous actor, he knows that it would be difficult to make a commitment and to start a family if he is shooting movies all the time. I read a book about him (by Maureen Paton) and it said that he didn't ask Rima to marry him because he said that he loves her, that's the most important thing and that is all what matters;)) well, it was something like this