You are missing consent. I am sorry that you don’t understand the concept. Vendors can choose to sell some items and not others. I’m sure that prostitutes may be willing to do some acts and not others. No real life experience.
I understand the concept of consent, and I realize that prostitutes might offer some services but not others; I’m just not aware that a, say, dime store vendor who has a bunch of things for sale could decide that some of them really aren’t for sale, such that if you take one of them away and put the correct change (including tax) according to its price tag on his register counter, you could be charged with theft. That’s what I don’t get.