If it's for my annual physical I wear my workout clothes - sport briefs under my nylon running pants and a lightweight polo shirt, no sox, and shoes I can slip off and on easily. This is for one simple reason: my doc has the staff weigh patients and take blood pressure out in a common area where there is no privacy. Weight control is a very important health issue for me so I want to be weighed wearing as little as possible. (At home, I weigh myself every morning in the nude.) Once I slip off my shoes the rest of my clothing only weighs a few ounces so the reading on the scale will be very close to my actual body weight. Once in the exam room its a simple matter to peel off the shirt and trainers and put on the obligatory gown. The instructions from the nurse are always to leave one's underwear on under the gown.
This topic made nme think back to my youth six decades ago when society in general and medical practice in particular were so very different. From my pre-teens well into my 40's I remember always wearing street clothes to the doctor, because once the nurse got me situated in the exam room and did her bit, the instructions were to strip down to my shorts, hop up on the exam table and wait for the doc. Everything after that - weight, history, BP, exam - took place with me (shivering usually) in just my jockey briefs. There was little modesty expected of male patients, and the doc was male, so why not make it easy and be nearly naked for him. There was also a practical reason for this practice, in my mind, in that the doctor could actually examine one's entire body, perhaps seeing bumps or discoloration or other indicators of possible malady that would not be noticed on a fully gowned patient. Back then, it was expected that the doctor would actually examine the patient, rather than simply go down the questionnaire ticking boxes on his computer screen.
I have to confess to getting something of a little thrill standing or laying there in just my shorts in front of the fully clothed older (usually) doctor, who had tacit permission to touch me everywhere. In my early teens it wasn't unusual to get a bit excited while stripping, then thinking very non-exciting thoughts while waiting for the doctor trying to calm my arousal. The only time the type of underpants I wore seemed to have any noticeable effect was during a flight physical by a new younger doctor. I was in my early 30s and the fashion then was bikini briefs for men. Mine were black usually and particulary sexy i thought. This doc took a great deal of time removing them for me as I lay on the table for the palpitation part of the exam and the bits that followed.
I guess the long and short of it is that for a real exam, opposed to a play exam, what I wear really doesn't matter anymore. We get our 15 minutes with the doctor. the codes go into the computer, and if he actually looks at any part of our bodies we should consider ourselves lucky and trust to luck and the Center for Medicare Services that he hasn't missed something potentially serious.