I never even saw a gown for an exam until I was 17. Before then I always saw our family doctor at his private practice. At those exams I was always just down to my briefs, or totally naked for the entire exam. I think probably around 10 or so I could keep my briefs on, and just lower them for the hernia check.
From when I was about 6-8 I had school physicals in a mobile medical unit, a trailer or RV, which came to our school. The first year, I was just in my briefs, in the other two years I was either totally naked or just in my socks, (which made me feel more exposed than when wearing nothing at all.)
When I was 17, our family doctor retired, and we went to a small practice with three or four doctors. There, if I was told to disrobe I was given a gown. But, I've also had several exams there where I was only told to remove clothes as they needed to examine certain areas. Sometimes just my shirt, one time I was naked below the waist for a prostate check, but kept just my shirt on.
In medical studies I've participated in, I've been in various states of undress. Shirt off, pants on. Naked below the waist. Just in underwear. A couple times when I wasn't expecting to have a physical I wasn't wearing underwear, so I was just naked. They don't always have gowns. And, I've also been asked to take everything off, and put on scrubs.