Most men are incapable of romantically loving someone without sex, but they are capable of engaging in sex with someone without romantically loving them.
Thanks.
For the 2nd portion, yeah but that's the case with most humans regardless of gender.
The first portion is interesting. It's a generalization, but there's truth to it. I think a lot of the push-back is when people confuse the presence of truth with "true" or "the truth". There are plenty of anecdotes of the devoted husband to go along with the cheater. I'm not up on the current data to assess "most".
But if you want a glimpse into the male psyche:
Hormones and puberty do weird things to animals. Your puppy starts inexplicably humping your leg, and male humans masturbate into gym socks. It is a humorous side of evolutionary forces. Although we humans are gifted with reason, there's a lot of evolutionary force (which is to say: nature) for it to overcome.
That force is no small thing. Look at some examples for women. The "biological clock" manifestation can completely override previous (or even current) opinion(s) of having children. "Nesting" behavior is another, or even simple emotional variation as part of PMS. Women understand hormones and fluctuations.
Our hormone is testosterone. It fluctuates too, and it's built in. Part of our literal nature. An irrational desire to stick an appendage into something (or create some facsimile of the experience), because hormones. Humorous sides of evolutionary forces? That's the one we got stuck with. You think guys are happy about having to go to the ER because they got their pecker stuck in something?
Consider it sympathetically for a moment. It sounds absurd on the face, but think of this hormone-driven behavior as our "PMS". We don't get it monthly, we have it all the time (it fluctuates too, of course) and it's not completely uncontrollable. There's variance across the spectrum, and some of that is captured on this site.
But independent of all that is a human need for intimacy, which includes men. I'm not sure you've weighted this properly in your hypothesis. I, like most men, have jumped through the hoops because there was sex at the end. But I also have loved 3 women, and knew it before becoming involved. The first two didn't work out, but I married the 3rd (almost 30 years ago). Sex in those 3 instances was never simply hormonal, or carnal. It was part of romantically loving someone. It fulfilled intimacy. It wasn't the reason I loved them, or the reason I love my wife. We'll eventually hit an age where our junk stops working. I'm ok with that, because sex isn't the reason I love her.
But I'm just a sample of 1.