Ruwrak said:
I know girls who pull these things as well. Don't generalize me along with them
Steppin back to answer your question:
"Because they got a no, but can try for a yes" fits in.
And because (most) people (like that) like wallowing in self-pity and hoping for a bone of any kind thrown to them.
Basically ignoring and moving on is an option
This basically. There are desperate, pathetic people encompassing both genders. This guy obviously has, um, little understanding of social interaction, and social interaction with girls in particular. While I don't want to sound like I'm taking his side (because I'm not) this doesn't necessarily make him an arsehole. Keep letting him know, very clearly, that you are not interested. However, extending the hand of friendship, and giving him some constructive advice on how to sort his life out, might do the world of good for him, and if his getting over himself gets him off your back, then it's good for you too.
Edit: Plan B, if that doesn't work... just walk away. I foyu being around him will only ever make him more obsessive then the best thing you can do for the both of you is just stay away from him and hope somebody else can knock some sense into him.