WHY DO GIRLS I LIKE SEE ME AS A BROTHER TYPE?

I am a college sopre who is single, I am 6'1 1/2 and weigh 210 lbs, with 10% body fat. I exercise regularly, have a 4 pack, and can bench 215. I make friends with everyone I meet, I've been told I'm funny, I'm a pretty laid back guy, and I am very well mannered if I say so myself. I have a 3.2 GPA on a 4point scale. Girls like my dimples, too. I have even caught girls sniffy me with their excuse being "I'm sorry, but you smell delicious" and they always call me the "perfect guy"( I hate being seen as a paragon). But yet every time I tell a girl I like her or ask her out on a date a get a blank stare like WTF, followed by a flat "no." Why do girls do this? What should I do?