Have you ever had sex before marriage? (Question for Christians)

I waited until I was 24, and ironically I wasn't even in the church until I was 20; so really only 4 years of any possible moral reason. A couple websites claim that 90% of Americans have premarital sex. I've only had sex with that one girl, and we aren't together anymore, but I'm just curious why so many Christians engage in premarital sex even though so many churches preach against it. For me, it was just something I had never done before and felt like I was the odd man out.