you know, i'm not saying this is the case here, but i've had a few guys complain to me about the "always a friend never a benefit" thing, and invariably these guys always had some obvious, glaring thing about them that was .... ew. and invariably these things were addressable/preventable/fixable.
now, i'm not one to gauge a guy's whatever

but if i in my 100% hetero viewpoint can recognize something needlessly gross and mule-like about a dude, then imagine what a healthy hetero girl would be thinking?
how does this apply to the op? well, this may sound harsh, and like i said, i don't know the op at all, so i'm not saying any of these apply to him, but this is sorta my generic "straighten up and fly right" speech

...
1. how's your hygiene? no, smelling like a jock strap is -not- manly. how's your breath? is your skin greasy? do you smell like socks?
2. how's your wardrobe? yeah, clothes - if the best thing you've got was purchased at walmart, then count yourself lucky that someone's even gonna cry on your shoulder.
3. how's your "presentation"? are you fawning, desperate and preening? or are you confident, solid and intelligent in your communications? think of every interraction with a potential "buddy" as a job interview. it's nothing to do with being "a nice guy" or not, it has to do with having the right qualifications for the position(s).
4. how's your general attitude, outside of your "maneuvering"? are you a positive person? do you have a cool, intelligent, unique outlook on things? do you like to talk about ideas and concepts constructively? are you confident enough in yourself to praise other people you see without reservation?
or are you cynical, insulting, petulant, whiny, intimidated, dumb, superficial, egotistical, etc.? which one would -you- rather talk to? and don't think that just because you are the chosen receptical for the girl's estrogen symphony that means that she's not listening to you talk about other stuff. most girls over the age of 18 like to talk about a lot of things more than their problems, but they like to talk to someone who they think actually has something to say.
5. do you exercise? so you try to make yourself the best you can be? or are you a fat sack of slack? i know, it's harsh, but think of it this way. look at yourself in the mirror, naked. would you want you? if you can't say yes, then it's time to hit the iron.
i guess i'm saying it this way because now that i'm back at school, after being out so long (and it's a school that is really well known for being very heavily skewed-to-the-male-side population-wise) everyday i'm seeing dorky, nerdy, clueless guys make utter fools of themselves trying to impress a girl enough to make a "connection". it's embarrassing

.
it's not the girl's fault that she's not into you (And again i'm not directing this to the op, but more toward the belly aching "i'm such a nice guy and all the bad guys get the girls waaaah" guys.) there's something that you're doing wrong, and you keep doing it, hoping for a different response. that never works.