Because how do you even get consent from someone who happens to find a sex workers post that has sexual images on it? Are they going to add a system in place for that and even then how long does consent last is per post or per account? There's nothing there besides don't share without consent.
But if a sex worker or nsfw artist makes a post with that content is it now against the rules because consent wasn't asked for by the 400th random stranger that happened to stumble upon the post/account? Like we have the features that hides the image so you don't see it which is all you need.
Adding more to it like the guidelines want makes it incredibly vague and open for bad faith actors to abuse for censorship reasons. Same goes for the animals guidelines, everyone knows that will just be used to ban furries from here because those pushing for censorship will just call us zoos and ban