Probably because it's not "manly," ie, it's sweet and fruit flavored. I don't know about the rest of the world, but in America the stereotype is that tops are masculine and bottoms are feminine, and that sweet drinks are feminine.
While I could imagine there being some kind of "drink code," meant for clandestine flirting and hookups, in which different drinks mean specific things similar to hanky code, I could find no evidence of this being the case.