Guessing that most here read romances. It has many readers, more than most others, and yet is not as respected as like mysteries/thrillers/etc. Why are romances held up to ridicule to the point that some don't want to admit they read them or want to hide covers? It's not like a mystery necessarily feels like-- oh yeah, that's how it'd be.
Some believe that passionate love, such as is often in romances today, would have been unknown in historic times. Well, it was in the Bible in books like Song of Solomon, "My beloved is mine and I am his; he browses among the lilies. Until the day breaks and the shadows flee." Sexuality, whether euphemisms or not is not required in a romance novel, which is about a type of relationship that goes beyond logical explanations. Closed door or open, the options romances have no rules for that.
It is true that romantic reasons for mating are a bit of a luxury. If you are struggling to put food on the table, have land you must protect, need the proper progeny, you might have fewer reasons to wait for the perfect love. Marriages have often been about cementing families or gaining power. In the most primitive times, the best hunter, the woman with the most fertile body, tribal connection and bartering likely led to the most marriages.
Whether putting romance in a contemporary or historical period, there are cultural things to consider-- rules that must be obeyed if the romance is to be believable. Writers research the practices of other times and try to stay with what could be true today. Age though is no barrier to romance.
Some would argue that to think of romantic love is unrealistic. Concentrate instead on more practical values; but to what exactly would they find to replace it? Money, fertility, family, education? And would those values last any longer or give any more satisfaction?
Studies have shown that many who read romances are working in stressful careers, have good marriages, but the romance is a moment of escape, as well as a way to get their own juices flowing after a stressful day of dealing with a sometimes harsh reality. Nothing wrong with some lovely escape, and I personally feel proud of writing romances, while making them feel as realistic as possible-- but always with what life does not guarantee-- a HEA.
For anyone at Facebook, interested in discussing more like this, I have a group that is open to the readers and writers where ideas can be explored. Check it out; and if it looks interesting, join-- https://www.facebook.com/groups/213424252693223