Fair weather friends?

Something I don't, and never will, understand, is people who are only your friend when its convenient for them.

Either my "friend" hates me or I'm not his friend at all. I'm only there as a friend by proxy. He only cares to hang out if other friends are there. I've been begging him to hang out for weeks and get lame excuses, or none at all. Just a flat "Sorry, maybe some other time".

Frankly, I'm not even sure why I keep trying other than I don't like to think the worst about other people. Unless directly insulted by someone I try to keep giving them the benefit of a doubt, but how much is too much? When do you have to decide that a person isn't your friend at all?

I have other friends, certainly. I don't -need- more and more, and losing one won't be the end of my life. But don't other people need friends too? He might infuriate me sometimes. I'm sure I piss him off from time to time. He might get on my nerves, I might have shit to say about or to him, but everyone has some kind of problem with everyone else. No one likes everything about someone. That's not natural. the whole point is being friends and accepting someone despite the things you might not like about them. Its damned difficult when the second party doesn't even try, though.

I'm getting tired of being brushed off and treated like a nuisance. Still, how much is too much?