In short human nature of homoeconomicus

Various arrangements which are described as ‘sugar daddies’ and ‘prostitution’, and more besides (such as polygamy) are prohibited arbitrarily, classified as ‘not marriage’ (as though the State has any business classifying what contract counts as what); and they actually reflect some adaptation to the circumstances of the people involved. Maybe sugar-daddies and prostitutes would not be as popular under a regime of laissez-faire; but whether or not this is the case it is obviously a preferred situation for many people in the present. The war-on-sexual-contract is as pathetic and mindless as the war on drugs; and possibly just as damaging – more people just tend to take it for granted.