I've never understood what sex has to do with marriage. I know more married men who are getting NO SEX now that they are married.
But seriously, I agree with lendaddy here. It isn't truly a religious thing. It's a moral thing. But as often is the case with morals, morals are usually out of touch with society, and in this case, hormones.
I actually think marriage itself is a larger concern than what proceeds marriage. And having children. More and more people are ill-equipped for either IMHO.