I don't think one night stands are natural either An C, just for the record, and certainly not desirable!
But those who didn't have the fortune to meet an enduring Mr Right - or Miss Right as the case may be - when in our youth, either live a life of celibacy or have to survive life as a 'single', which is not easy in any respect; and may require a good deal of juggling of priorities, possibilities and so forth (which is how the thread started). It doesn't pay in that situation to be too po-faced about it all. A sense of humour is a very necessary survival technique, in my experience...
Those who have long been happily or at least satisfactorily married can count themselves very lucky in life; they don't know the half of it!
And since the good men almost all get married young, and affairs with someone married are even less desirable than one night stands.... well, you get my drift.