Sex can be recreational and fun. Although the kind of sex that you mention (the complete absence of feelings) usually happened when I was seriously inebriated...
Hubby and I used to swing. We have had an open type relationship. We have engaged in 3somes and moresomes. It was fun. Just like swimming or skiing or dancing can be fun. But when done - everyone goes home and either there's a personal connection or there's not - but we're all heading back to our lives.
Sex can also be incredibly emotional and connective. I have experienced that "want to crawl up inside you and be part of you" sex with one person - my hubby.
I don't know if there's something inherently WRONG in my brain chemistry - but I don't need love to have and enjoy sex. The two are not intrinsically connected for me. Sex is a phyiscal act that is fun and satisfying.
But what happens between my hubby and I... is much more.