I really don't understand it, but until he died, I used to take my Dad to his medical appointments. He was over age 65. When he was in the examining room, I was there, too and he would only take off his shirt. If that. Every 6 week - 2 months he would have a follow up visit, monitoring blood-pressure and blood-sugar level.
I always stripped down to my underpants when I went for my physical exams. That way the doctor could check everything with ease and we wouldn't be wasting his time fumbling with clothes. He could also see if I had skin rashes, scars swelling of joints, etc. Now-a-days doctors can't be wasting time when they see a patient. They have 15-20 minutes to get you in and out so you need to be ready when they have to give EKG, do knee reflex checks, draw blood, listen to heart, lungs etc.
When you are fully un-dressed, the doc can see everything and quickly do what he/she needs to do without fumbling with clothes.