The answer, IMO, is that some single men know better what the average woman wants (or at least the type of woman they
typically date wants) than their average married counterpart. I think I know better, specifically, what my wife wants, but I wouldn't put myself in a pick-up contest versus a single man who is considered to be somewhat highly dateable.
All of that said, lots of single dudes are antisocial losers and I would take the average married dude in a "what woman want" contest over a single dude. (That's a result of the fact there are a certain number of unmarried losers that are dragging down the single average, as much as anything.)
I chose married.