Good question @SouthernAnn and I wish I knew, as I have long wondered as I have been lucky enough to have worked around the world and except for a rare, few occasions never been offered a gown other than in an hospital and that was to walk around the hospital.
When I went for my first physical in the States I was given a gown, told to completely strip and I dutifully put it on. The second time I did not bother and the nurse was most insistent even I told her that the dr would be seeing “my bits” anyway when she examined me, so what was the point of the gown. Once my wife and I were booked in to have our physicals after each other and the nurse was quite put out that each of us would be present at each others physical.
Compare that with when I worked over on the continent. There a lot of countries demand a visa and part of the process is to have a chest x-ray and a medical. As a family we went along to the local hospital for the x-ray. We were shown into a waiting room which has 3 or 4 topless people waiting sat on chairs and told to strip to the waist. Coming from a more conservative background my wife and daughter questioned the request seeing that there were others in the room, and the nurse confirmed the request so we all took our tops off and my teenage daughter drew the short straw as she had a summer dress on so it was knickers only, and there we sat waiting to be called. It would never have happened in the UK, but everyone seems to take the semi nudity in their stride and there was no embarrassment.
A few weeks later we all went along to see the doctor appointed to do the exam. When we got there we were shown into the doctors outer waiting room and told to undress and having got use to the countries medical system, we duly conformed. A few minutes later a couple and 2 teenage boys came out and casually got dressed whilst we waited to be called, I remember that at the time what I perceived the absurdity of chatting casually to strangers when we were all naked . When we were called in, the medicals were pretty standard and when we left the doctors there was another couple sat waiting.
Over the course of our stay, we had to repeat the medical process several times, and I loved the informality everyone took to being naked in front of each other and the municipal saunas were a joy.