Quote - They can't control what the end users of their models do with them and can't be held responsible for it.

It's not the users the various vendors worry about but rather companies like Paypal and such which have rather insane policies regarding anything with even a hint of 'porn.' Some of them will refuse to do business with such vendors or charge outrageous premiums or simply ban your account (and steal your payments.) There are niche companies that don't mind what you do but naturally these are also the same companies that deal with real porn and few Poser vendors wants to be slotted in the same category as 'Hot Bangin Pussy Ranch LLC.'