Why do people not have sex until after they're married or when they found "the one"?

First of all I'm not judging in any way it's just a question. I'm interested in knowing why people want to? Why do people like saving themselves for marriage or for the one they think they'll be with forever? I don't believe in that kind of thing because I'm a "wannabe hoe" and rather sleep and experience different things with different people and relationships before finding the one. I'm not too good with commitment. It would be good if I found the one straight away but that's not likely to happen especially where I live in the UK. So yeah, my question is why do people find it so important to find the one and only have sex with them?