Why do guys ask if you like them?

It probably means he likes you! He might be asking to see if you reciprocate his feelings because he's got a crush on you. It's also easier than asking you out; this way if you say no he can play it off. That's kind of hard to do when you ask somebody out. There's a small possibility this guy is just wondering though... boys can be weird like that! He might have been getting flirting vibes from you, whether you were or not, and is wondering if you're into him. Your choice on how you answer the question :)