Personally, As a friend to many guys and being one myself there are a few base reasons a guy does not call. I suppose it depends on his personallity, as to which he would choose to claim.
I might first state that most guys are conditioned to portray that he is cool and unattached or uncommitted to becoming attached. The best way to drive someone to you, is to make it appear that they can not have you. At least most guys think or believe this is a good ploy, to avoid getting thier hearts hurt and to act cool.
Secondly, in some instances, something happened or was said by him or you which made him feel uncomortable. He is embarrassed or scared that by putting himself in the situation again, he may come out looking like he is too soft, or too vunerable.
Personally, I feel that it is inconsiderate and a self indulgent, self serving game of "Cat and Mouse". In most cases, it may be in your best interest to just move past it and move on.
Here is the problem of pursuing him. Regardless of the reason he is playing this game, with you; He probably is deeply insecure and wants validation from someone, to make himself feel important. He really does not care how important you think he is. By pursuing him, you are validating him and are opening the door to either being compromised emotionally or physically (or maybe both).
You seem like an intellegent person, and you don't seem to have time to play these games. However the game is as old a "dirt". IF this guy is important to you, sit back and wait for a bit. Call him a couple of weeks later and go have coffee.
This neither validates him, nor causes him any discomfort if he is afraid he might have embarrassed himself, during the previous date. You dont appear too anxious nor like you are pursuing him, It is a neutral and safe situation for both of you.
Good luck and happy dating. Stay safe..