When you're single the incentives for being good at partner dancing are considerably higher than when you're securely in a relationship.

I went the opposite direction - from being a fanatical swing dancer while I was single to being completely uninterested in it after I met my wife. It was purely instrumental, in other words. And I saw the same pattern repeated with the majority of swing dancers both male and female. As soon as they were hooked up, it was see-ya.