Attractive boy:Hi! I'm famous and completely inaccessible.
Attractive boy:Hi! I'm straight, so the only serious relationship we'll ever have begins with a "b".
Attractive boy:Hi! I'm a douchebag, and for the most part you'll just be a really awesome fleshlight to me.
Attractive boy:Hi! I'm twice your age, so most people will assume we're related and that'll make any kind of PDA painfully awkward.
Attractive boy:Hi! I'm a lot younger than you. Jail anyone?
Attractive boy:Hi! I'm taken and/or blissfully happy without you.
Attractive boy:Hi! I'm going to friend-zone you. Good luck not developing feelings for me while I depend on you for everything except romance!
Attractive boy:Hi! I live on the other side of the world.
Attractive boy:Hi! I'm not even the slightest bit interested in you because you're too tall, or too short, or too skinny, or too fat, or too fem, or too masc, or too boring, or too outgoing, or I don't like your skin color, or I think your hair is gross, or some other reason that will make you feel like there's something or several things terribly wrong with you.