What is the appeal behind waiting for marriage before having sex?

I'm 17 and had sex for the first time with my boyfriend of (now) 3 months about 3-4 weeks ago. I cannot imagine having waited, and I also don't think I will be with him forever either. As much as I do kind of admire people who wait till marriage, or stay with the person they first do it with, I don't understand the appeal of it- if you've done this, can you please explain why? I personally just can't imagine it haha :)