This doesn't mean both parties are achieving equal sexual gratification when it comes to marriage or other long-term relationships. Other 2019 studies such as this German one find marriage has a negative net correlation when it comes to sexual satisfaction. Only single people with no current partner report being less satisfied with what goes on in their bedroom (and that's only because of less-frequent sex, the study found).
So who's actually having the best sex of all? Unmarried couples who live apart, it would seem. Not sleeping in the same bed as a partner every single night looks like the best recipe to have better orgasms.
Dr. Philip Hodson, the lead author of the Florida study, believes a possible explanation as to why women in committed relationships achieve orgasm more is because they "need more sophisticated touching than just your standard intercourse to reach climax". What he means by "standard intercourse" I don't know.
I have a couple of theories as to why sex with a spouse is better than a one-night stand. First of all, you're almost always drunk for casual one-time sex, and this is always in the wee hours of the morning when you're tired from a night out. People rarely have one-night stands that consist of a sober conversation and a 10pm bedtime. Sex while inebriated can be good sex, sure. But, like everything else (including boring conversation!), alcohol also seems to make things more interesting than they really are. What you consider pleasurable at the time might just be a regret in the morning. Sex with a long-term partner, on the other hand, is more likely to be "conscious" sex. You don't have to get hammered to be pleasured.
There's also a lot of guesswork to do in one-night stands, whereas in relationships you can be communicative about your likes and dislikes. Some people are really good at this guesswork – they know how to "read" a person's sexual desires off the bat and make exceptional one-night stands – but these Casanovas are rare.
Lastly, I think when you're in a long-term relationship you feel more empowered to give direction and take control. On a one-night stand, you're more likely to put up with things during sex that you don't really enjoy (like having your ears licked or too much focus going into your breasts, for example). Naturally, this factor is conditional in having a partner who isn't insecure, which can be another hard find.
As for one-night stands, what are they good for? You can't deny that there's a sense of euphoria in newness. Seeing and touching a new naked body is exhilarating. When sex is unfamiliar, it can be wonderful simply because it isn't routine.
Throughout your life, you're going to have good sex, and you're going to have bad sex. But more often than not, you're going to have average sex. I think that's the key in enjoying your sex life and orgasm frequency here, no matter your relationship status: just accepting that most sex isn't going to be mind-blowing.