i've thought about this a lot myself.
Seems like sex drive is something that is engrained in all of us, period. The desire to be with one person your entire life really isn't. Think about it, one is a trait that as evolved over millions of years and is one of the strongest drives that humans (or any other animals) have.
Choosing one person for your life partner is a much newer thing, and is NOT something that increases the survival of your DNA, what if your one partner was not fertile, etc. That would be weeded out through natural selection.
Seems like ONLY in modern times has this type of monogomy been the norm, think of tribal leaders they had TONS of women they had sex with. Same with biblical times, Abraham had a wife, but many other concubines with whom he procrated with. This seemed to be exactly what his "god" had in mind and it worked for him.
As far as loving people, I can love many, but there are some things within a relationship that are unique and special to the dynamic. I could find something similar with someone else, but it would never be exactly the same.
having an orgasm is different, you can have big ones, small ones, intense ones, less intense ones. I've had sex with a few people and different people just connect together totally differently. Had I gotten married at 18 I would have missed out on a whole ton of things that I am glad to have experienced. So now are you supposed to wait to get married until you get all of that out of the way, how will you ever know?
The main issues I think about are health ones. Sex can come with adverse health effects, that is something I am conscious of when selecting sexual partners for sure. I am not married, and not in a serious relationship, so I don't have to worry about the cheating aspect right now, but I have in the past and basically I just surpress the desire to fuck other women and make the best of what I've got. Sounds shitty I know, but come on, just because you are married some switch doesn't flip that makes your brain NOT want to bang other people! Its exciting. Who can deny that. Sure sex with someone you are in love with is great, a connection of sorts, special, all of that. But people can be married for 50+ years, that is a LONG time to go without any new pussy/cock, I'd argue its unnatural.