Most probable causes: 1. The guy's a virgin and is scared of taking the next step when cuddling. 2. He's some religious dude or something similar that holds him psychologically and makes him think he's more valuable than other people because of what he's doing(which is so messed up I'm not even sure I would know how to explain it). 3. Something else - it is possible that he has some personal reason which we cannot possibly guess, so it's best for you to talk to him about that. You should be open about this stuff.