How often do you think one night stands happen in America and for what reason mostly?

I had dinner with three female friends, two were single, 30 and 34 years of age and the third, a 45 year old mother of two and happily married. Came quite a bit of a surprise when all three stated that women DO NOT really go out to have one night stands or sleeping on the first date. They think ahead, always looking for the one, the right one for them. Were they all just being romantic? Am I a douche for being surprised? It’s just that I thought at least one of them would have a different view.