According to LinkedIn, thou shalt not:
i. Even if it is legal where you are located, create profiles or provide content that promotes escort services or prostitution.
So, even if it's legal, LinkedIn doesn't want anything to do with it. Because, why? Is this a misguided moralistic choice — because, let me tell you, there are plenty of people with Linkedin profiles who do thinks that are way more morally questionable than sex work. Or is this a legal thing? They're based in California, so perhaps there are laws governing what they can and cannot participate in, legally.
Either way, they need to check themselves first, because you can totally endorse someone in prostitution. Also, their loss, because innovative Silicon Valley sex workers have plenty of other ways to get the word out.