Sure, but like being able to own a firearm based on common principles that became standard after 1900 or buy medical/recreational marijuana (with a strange situation of Federal limbo on both: states going 'against' Federal law with more restrictive and less restrictive laws), even if only a few populous states make it illegal, it's hard to say "Hey, this is legal in America"

In any case, I don't see much reason for prostitution, accompanied by licensure and medical testing, taxes, and some oversight, to be illegal.

Being promiscuous hasn't been illegal, ever, and hasn't been a socially censured thing since the Sexual Revolution. Selling things and buying things without undue government interference sans political say in what kind of commerce a people can engage in for their own earthly ends is literally the basis of the American revolution.

Premarital sex has been the norm for decades now, at least three generations, marriage is no longer a social guarantee, the economy is doing poorly with homeownership and stable incomes for families out of reach of many in the first place.

The sex drive however, doesn't go even go away after infertility and impotence.