Nobody needs all that love or sex in life and besides one of them is just going to dump the other and then go into a giant crippling depression. Besides what if they have sex and “oops I had a kid involved” the boy leaves and the girl is stuck with the kid. Oh yeah that’s FAIR FOR THE WOMAN!
Humans are social creatures and we need one another. It doesn't have t be in the form of a lover. However, The best lives are ones filled with close relationships and the best memories are made with those we are close and connected to. For most people, Their live is better with a lover, So long as the people are compatible.