Good question, @John657. I don't know for sure, but I suspect it is two things. First, there are recommendations from the United States Preventive Services Task Force. You can look them up at https://uspreventiveservicestaskforce.org/uspstf/. The bottom line is that they don't recommend a lot of stuff any longer. Hernia and testicular exams aren't recommended, and, apparently they no longer recommend digital rectal exams. So, since the recommendations to check these things are gone, I think a lot of physicians feel that they don't need to get the patient undressed.
Second reason, I think, is the Nassar effect. If you don't know his story, I don't want to tell it, but it's available in lots of places, including here: https://en.wikipedia.org/wiki/Larry_Nassar. I think the fear of getting sued, or worse, arrested, makes a lot of doctors ask "why even ask anyone to get undressed unless I really need to?" I also think it may be related to increased emphasis in the business of medicine to improve patient satisfaction. Some patients will never go back to a doctor who makes them take their clothes off -- so leaving a patient dressed reduces that chance of losing a paying customer.
I like my patients to be as undressed as possible - at least down to underwear. This is not for any erotic reason, it is just so that I won't miss anything important. However I am not the one getting patients undressed - it is the nurse. I usually can't take the time to come in to a room, get the history, ask the patient to change, leave the room while they change, and then come back. My patient load is just too high to do that, so I usually examine most of my patients dressed.
To expand on this idea - I often say that it is not the young, cute, sexy patients who really need to get undressed. These patients are often relatively healthy and aren't hiding much. It is the old, fat, dirty patients who are the ones who really need to get undressed. A lot of badness can hide under folds of dirty, smelly skin.
Sorry, not very erotic, but that is real medicine.