Theoretically, the needles are supposed to go in a specific place in the areas where chi circulates, so it would seem the practitioner would have to see and feel the person to find the right place to put the needle -- can't do that through all that clothing. On the other hand, there probably is no such thing exactly as chi, it's something but we don't know what it is. Still, we only know what works by the historical practice of it and that practice has tested well in modern experiments, but a lot of people who practice acupuncture today aren't actually very well trained -- a lot of them are chiropractors and other practitioners who study a few weekends and get their certification because that's how the system works in the US when you're already a credentialed health care professional. Someone starting from scratch has to take a 4 year course in it and also study TCM. But even if you had taken off your clothes to allow better aim, some people do feel pain after acupuncture. I don't think it happens most of the time, but enough to have several posts just on this website. As with everything else in life, some are just better than others at what they do, and some patients are just more sensitive than others as well.