Just because it doesn't work for some doesn't mean it doesn't work at all. For example my parents were in a romantic relationship for 5 years before getting married and never had sex once until after they were wed and never once did their relationship beforehand struggle.
And that's not counting people like asexuals who can be in a loving relationship their entire lives with their partner without ever having sex.
Thats absolutely different.
Some people for religious reasons or moral reasons want to wait to have sex till they get married. Personally i think its stupid, you learn alot about a person when having sex, but thats besides the point. Yes they chose to hold off on sex, thats fine but they didnt go without. They just waited. And after they actually had sex Im sure they didnt say, you know what, we did that it was fun but lets not do that again. No of course not. They had you right. lol.
Sex is natural, sex is a way of showing you care about somebody and a healthy sex life is pretty much vital to a happy relationship.
But anyway, we are a bit off topic with this.....