Gahhhh! Sex is a HUGE deal! At least to me anyway. It's getting NAKED with somebody else -- sharing your BODY with somebody else! You're vulnerable, in so many ways -- emotionally, physically, virally -- aside from every other reason, it'd seem to me that if you don't really know a person you're getting ready to have sex with, you don't really know you're not gonna get anything.
Which is not to say an STD is the end of the world. Just that I'd rather not have one than have one.
And as for kissing --
I agree, it's less of a big deal. Everybody's read that poem that has the line in it, "Kisses aren't promises." But I guess I kind of treat them that way -- there's the implicit implication that you're interested, in the person, in getting to know them more, etc., etc., etc.
Besides. I like boys. I want them to feel like when I kiss them, it's hot stuff.