Eh, the Muslim world is different than the West, so it shouldn't be viewed in the same way.
In Islam, it's suggested to get married as young as possible, so that you will be less tempted to have sex with random people. but in today's society, you can't really do that, so pre-marital sex is becoming more and more common, even in the Muslim world.
again, it also depends where you live. I am Muslim, born in the US. I decided to try to wait until I was married, but now at the age of 23, am giving up on that, and gonna shift to wait until I fall in love with a girl instead. My cousin, on the other hand, who was raised by the same family in the same way, decided to be a normal guy, and get laid whenever he feels like it (I mean, when he is able to). we both believe in the religion, we just don't follow it completely.
the same would be said for a Christian deep within a very strict (and in my opinion, very stupid) interpretation of Islam, like Saudi Arabia. They can't really do much, regardless of what they believe.