Why do these guys tease me for being a virgin? Also, they're British?

I'm 16, and when I went to Britain and hung out with these 3 guys, (I've been talking to them for a long time, but it was my first time meeting them in person, ages 16-17) they treated me differently than the way guys did back in the US (where I live.) I guess it's because of the area they all grew up in, but most teens there our age already had sex, smoked at some point, and drink. So, when they found out I was still a virgin, it seemed to totally change their view of me, and it was as if I became some sort of target for teasing. They began making countless jokes and got more 'touchy,' (excessive hugging, a little bit of groping, smacking my ***, etc.) And I mean, I'm not some prude who rejects any little sort of sexual actions, but I don't know.. it became a bit too much. So, why do they like to tease me so much about being a virgin? I've had a little bit of friendly teasing at home, but not to this extent. I just don't get it. A guy's opinion on this is preferable, but anyone is welcome to answer - thanks!