I see it as a pure protocol thing – get naked to prove you are not a cop. There is nothing nuanced about it. I still don’t get it – a cop can put his life on the line of fire, but he would not undress in front of a lady!? Maybe it’s a whole dance on who makes the first move.  In my earlier encouters I would get the hint, but act on it only partially and would keep my briefs on, then a lady would say “do you want to get COMPLETELY comfortable?” So, I do it now without an invitation, but only because I want to put provider at ease ASAP. But nothing comfortable or erotic about it either - getting undressed while provider does nothing and waits for you to get completely bare, like you came for your freaking yearly physical check-up. (well, unless you actually play out a fantasy of screwing your nurse or a doctor.)
How about SHE strips for me, while I'm sitting in a chair checking her out, and then she does the number on my zipper. That’s comfortable! After all we don't pay good money to feel awkward, we pay it to feel good and pampered.
Nevertheless, there is always protocol at first visit. If you pay the subsequent visits to a provider, it becomes less “formal”. So, if you are absolutely turned on by a woman undressing you or blowing you thru your flyer you may need to do two visits for that.