Most Helpful Guy
He just sees you as a friend or enjoys the flirting
Most Helpful Girl
For me there are two possible reasons.
1. He's scared that you'll reject him. Believe it or not guys have feelings too and if he's truly interested in you, just the thought of you saying no would make him upset.
2. He might not just be chatting you up. As likely as the possibility that he really likes you, that chances that he's talking to other girls isn't completely off the list. I've had guys tell me bull that they like me and that I'm the only one they talk to, only to find out from their friends that, that's a lie.
So my advice for either scenario would be:
1. Tell him how you feel. It's the 21st century. You shouldn't have to wait for him to make the first move. If you tell him that you like him and says he likes you too then bam you're together. Alternatively, if he says he doesn't feel that way at least you know not to waste your time.
2. If you find out that he's also chatting up other girls, move on. He's NOT worth it.