When I am giving a professional massage, I want to focus on the job,professionalism, and satisfaction, both for me and the customer. Thus I see no need for myself to be nude. More importantly, I see no need for the customer to massage my very sensitive nipples, thus possibly distracting me from doing the main job. I can't say that it has never happened, because occasionally I am so focused on my work that I am just not paying attention, and before I know it the customer has broken the barrier and caused me to erupt in cum. Thankfully, I still have my clothes on.