Over the course of history, the "shoulds" and "should-nots" of sex have changed dramatically. There have been times when sex was not discussed in polite company, times when women were believed merely to tolerate the experience, times when engaging in sex before marriage was considered scandalous, and many other permutations as well. Now the should-scale has tipped in another direction. We are all - women and men, both - expected to want and crave sex, lots of it, whether we are married or single or in some unclassifiable state in between. During each historical era, the prevailing view seemed natural and true.
In her widely-read essay, "Sex is not a natural act," Leonore Tiefer put it this way:
"The modern view of sexuality as a fundamental drive that is very individualized, deeply gendered, central to personality and intimate relationships, separate from reproduction, and lifelong (literally womb-to-tomb) would be quite unrecognizable to people living in different civilizations."
The desires of many contemporaries do, in fact, conform to today's new sex-suffused norm. Theirs is not a forced fit but a genuine one. For those who not only like lots of sex but can readily find compatible partners, these are the best of times. (Although, with AIDS still unconquered, these are also among the riskiest of times.)
The dark side of the new norms, though, is that they leave little room for people with different sexual profiles or opportunities. For those would like to have a sexual relationship but don't, the relentless celebration of all things sexual must be particularly painful. (Thanks to commenter Incel for reminding me to acknowledge the community of Involuntary Celibates. You can read more in Chapter 9 of A History of Celibacy.) Those who simply care less - or not at all - about sex are marginalized by contemporary sexual norms, too. In other eras, they may have felt virtuous. Now, even the most contented among them must wonder at times whether there is something wrong with them.
The relentless feting of sex and the implacable sexualizing of society has shaped and strengthened a particular stereotype of singles - that their lives, more than those of married people - are driven by sex. Singles, it is believed, are always looking for sex but not finding it, or indulging in too much of it for their own good, or they are spectacularly bad at it, or they are such cold fish that they could never enjoy it, or - well, think of something damning, and it has probably been said about singles. All of those criticisms really are true of some singles. But here's the point: They are also true of some married people. And as a generalization, mindlessly applied to a whole swatch of people, not one of the caricatures is accurate.
When it comes to sex, people who are single have been set up. The group to whom they are compared does not consist of real married people but idealized ones. In the matrimaniacal picture in our minds, married people - simply because they are married - have magical access to perfect sex. One spouse's wish is the other's desire. A partner is always there, willing and able, never too tired, never not in the mood. Each spouse wants just the same amount and kind of sex as the other, and at exactly the same times.
Of course, if that were true, a lot of marriage counselors would be out of a job.
So yes, there are challenges around sex for people who are single. But do not believe for a split second that getting married will make all of your sexual dreams come true. Sure, there can be tremendous rewards for partners who are sexually compatible and who stay that way for the duration. But if and when things fall apart - as one person wants more sex and the other wants less, as one wants to experiment and the other is appalled by the mere thought of it, as one or both become bored or even hostile - being married can be even more daunting than being single. Especially if there are children involved. Any two people, married or not, can work on their relationship and their sex, and get counseling if they are so inclined, but when all efforts prove futile, married people are entangled in a way that singles are not.
It is not even true that getting married means that your sexual experiences will become less risky. A review of all available research, including studies of people of different races and sexual orientations, came to this conclusion: "practicing unprotected sexual intercourse with a committed relationship partner who is not tested for HIV appears to be a major and unrecognized source of HIV risk." When a relationship becomes close and committed, partners seem to believe that it is therefore safe. People whose relationships are just beginning are more cautious. Counter-intuitively, they end up better protected.
I'll end with my usual disclaimer. I'm not saying that you shouldn't get married if that's what you want to do. I'm not saying that marriage can never succeed. But I am cautioning you to beware of the marital mythology and the baseless stigmatizing of people who are single. Don't believe that singles are more self-centered than married people - they're not. Don't believe that you should be governed by other people's ideas of how you should live your sexual life (or any other aspect of your life). Live the life that feels authentic and fulfilling to you. No matter what it is, there will be challenges and rewards.