I have read that Millennials have less sex because of the ready access to online porn. I can see that from all the internet sex forums out there. Many men are living their sex lives online. Why shower, shave and get all dressed up only to be rejected by every girl you try to meet? Just fire up the old PC and masturbate to porn and you are done with no muss or fuss.
I was born when there was no internet, cable, or color TV. There were exactly 3 networks in black and white. Married couples on TV slept in separate beds and you could not use words commonly in use today like butt or ass. You could not show a bra on TV even when advertising them. We learned about sex the right way, in the street from ill informed friends.
We did not even have anything to masturbate to or to form a fantasy. All we knew about was vanilla sex which was intercourse. Oral sex on woman was considered gay by many and who knew that there was more than just the missionary position.
Despite this, we had a lot of sex. We had no choice but to go out and find women to have sex with us. We did not have a lot of options for fun, and sex is free. I am married 44 years and 30 of those years was lived sharing my wife's girlfriend who lived with us. To say that I had a lot of threesomes over that time period is an understatement. We had group sex and/or threesomes with most of our friends. We got married at the end of the hippie years where there was free love which meant a lot of sex with stoned people. That just carried through in my life. I knew I was poly since I was 11 and had two girlfriends.
We had to make up our own fantasies unlike the ready made ones you can find all over the internet almost word for word on each site. If we wanted sex we had to actually go out and meet girls 3 nights a week. For my group of friends, both male and female, looking for a boyfriend/girlfriend was the weekend activity. STD's were pretty much limited to prostitutes back then and the birth control pill gave woman a new freedom to have casual sex just like the boys did.
As far as I knew, there was a lot of sex going in my day, at least among people that I would be drawn to as friends. I now live in a retirement community that was written about all over the world due to the amount of sex going on here. We have swinger clubs, key clubs (wife swapping), meat markets where women fight over men since they outnumber then 10 to 1. Women would go to a car, have sex with a guy, return to the bar and do the same with other guys. When you know that the end is near or you have a fatal disease, you tend to want to experience as much as possible. People get arrested for public sex ever few months. The only old people not having sex are those that cannot medically do so. My wife and I have sex twice a week on average and are still into fetish play in our mid sixties.
With all the forms of entertainment available these days vying for your free time, it affects the amount of time you devote to sex. For us, sex was our main form of entertainment and on a fixed income, is still the cheapest way to have fun. Perhaps some younger people will let us know how it is with them. Of course my opinion is very subjective since I lived in an ethical non monogamous marriage and tended to have friends who also did not have traditional marriages. Sex was a big deal for my generation even though it was not talked about like it is today with forums in which you can share experiences anonymously.