My reasons for waiting (just so you have the other side too *snerk* and yes, I'm 34 and still a virgin...)
1)Don't want to be a notch in someone's bedpost (that's not saying I haven't seriously considered having sex a couple times, I'd be lying if I did)
2)Marriage to me is the sure commitment I'd want first - and yes I know the 50%-of-all-marriages-fail statistic, but hell, if my parents can stay together for 35 years and counting (their most recent anniversary - two weeks ago - was #35), I have a chance of making something last, should it actually happen
3)This one might sound odd, and I can't really explain it... but I want sex but I don't... I mean, I know the reality of what a first time is likely to be like, and though I might have romantic notions it's not completely a rose coloured glasses kind of thing. Yes, I'd like the silk sheets and the candles and a slow seduction, but...
I'm probably not making any sense, you can just ignore this point