People get into relationships for sexual reasons, no?
And then they get tired of eachother. Ive realized that some people don't like the person they are with very much. It's just too much work to switch them out, and you lose other things you want (like children, the house, money etc) if you break up with them. And you have to find someone new, which is very difficult today for a lot of people.
I wonder if even most people are slightly unhappy with their partner and they don't feel emotionally connected.
So I don't think it's wrong to skip all that and focus on great friends. But friends often get into relationships and you lose out on the friendship when that happens.