For men, it makes them feel ashamed that they have it because they think it represents immaturity or something along that line. For women, it makes them lie that they have it because they think it makes them less of a slut.
For the religious and/or conservative, having it makes them believe they're imbued with magical powers, which may remain ONLY if they lose their virginity in marriage.
College Whore: I still have my virginity!
College Professor: I still have my powers!
Parker: I took Christina's virginty.
Alex: God damn you, I wanted Christina's virginity.
Parker: Haha, sucks to be you.