To the extent that sex workers are objectified, it is a direct result of misogyny, which teaches that it is acceptable to treat women as objects, and capitalism, which teaches that it is acceptable to treat workers as objects. At the confluence of these two industries we find pornography.
That said, I believe it is possible to do sex work in a way that is liberating and not objectifying, and in my opinion the hyper-fixation on the objectification of women in pornography is itself a result of misogyny in our culture. Every industry objectifies and mistreats workers, so why do we discuss this issue so frequently that the term objectification is practically exclusive to pornography and related contexts? In my view it is because patriarchy requires women to be “pure” and “unsullied” by sex so as to maximize their value to men. The issue gets subconsciously mixed into genuine concerns for the well-being of sex workers. Together these impulses often lead to paternalistic and unhelpful “solutions” like arresting sex workers, or FOSTA and SESTA which claim to be for the protection of sex workers but according to the vast majority I’ve heard speak on this issue are extremely harmful to their livelihood and wellbeing.