When I wa a child in France in the 50's, normally it was the doctor who pulled down the brief when he wanted to look at my genitals.
When I became older as a male teenager, it was less fequent except at school physicals where the female doctor or the nurse did always pul down herself my brief at middle school. And It was not a question at high school since we entered already naked in the examination room after undressing in the adjacent locker room.
At university or great school physicals ( the equivalent for american citizens of the colleges), the doctor asked at us to pull down the brief for a glance on our genitals
At doctor's offices, about since I have reached 14 age, the doctor male or female asked at me to pull down myself my brief but sometimes a doctor could think that my brief was not enough low and would lower it more until ankles.
At military physicals before induction and for induction, we were stark naked but during military service if we went to see a military doctor, it was frequent that this doctor pulled down himself our brief just to have a look on our genitals or our buttocks or check our spine.
After as an adult either at job physicals or at a doctor'soffice, I have been always asked to pull down my brief when necessary when I was not told to remove it.