Sex before marriage, eh? That's been flogged to death, by every and any religion, faith or belief.
1) We all have our own opinons on this subject, one is not better then the other. Yours will be better to you, because perhaps you can see something that no one else can see.
2) I don't believe in sex before marriage, now isn't that amazing a teenager who hasn't had sex. Golly gee wiz. Family units have been around as long as men and women have. They would have had to come from somewhere, some belief. I have read a lot of different scriptures and different things on this and I believe that an ultimate Creator made sex for marriage.
3) Just because it isn't written in your 'bible' or book of scripture does not mean it wasn't their in the beginning. Especially the Christian bible. There have been so many errors and mistranslations and omissions and additions to it, whose to know what it was originally.
4) I've seen marriages were the couples have had several partners beforehand and 90% of them aren't happy. Why, because both of them have other sexual partners and because the current spouse doesn't raise up to those so-called standards, they aren't happy. By having multiple sexual partners you are setting yourself up for dissapointment anyways.
5) I think it is a pretty neat and wonderful idea to save something so special for that one person. Think of it, there are many thing you can give this spouse, but you can also give those to other people, you can only give your virginity, your chasitity, your pure self to ONE person, that's it, after that it's gone, shouldn't this be the person you want to spent the rest of your life with.
6) Why should it be in marriage? I think marriage, as I have said, was ordained or put together by some ultimate creator, that creator made marriage and instituted the rules for it.