I'm worried that if buyers demand to practice in secret, it becomes practically impossible to regulate and for sex workers to implement proper occupational safety practices. For example, security guards to protect them from violent customers.

In France, it's a bit more complicated.

According to the law anything implying money with a sex worker can be considered as pimping (which is obviously a criminal offense). You have a friend who is sex worker and they buy you a drink ? You're a pimp. You're a sex worker and you want to rent a flat? That's gonna be hard, because your landlord could be considered as a pimp.

Even banks refuse to open accounts to sex workers. A french porn actress (Khalamite) is an activist on the subject and made a YT video about that a few time ago.