I'm sure that, in North America, exam gowns are used primarily for the protection of the medical staff from patients who don't understand that such individuals - and many others in society - are readily immune from erotic thoughts and behavior at the mere sight of a naked member of the opposite sex, if they choose to be in a setting where such behavior is uncalled for. The million or so of us who practice nudism in an appropriate public environment are witness to that.
I enjoy a sexual tryst as much as anyone can, yet, even as a relative amateur, have inserted suppositories, given enemas, and changed diapers in fetish play with opposite sex individuals without becoming aroused. The pleasure I obtained in accommodating their fetish desires fulfulled each of us quite sufficiently.
Our general North American culture engenders much of our thoughts about nakedness. For some, it doesn't raise an eyebrow. When on a business trip to Stockholm in '79, I flicked on the TV in my hotel room one day and was astounded to see scenes of fully nude young gradeschoolers of both sexes simultaneously using a shower and same washroom facility. Not understanding what I was viewing (or the accompanying Swedish commentary), I asked a friend at work the following day and had it explained that, in years past, Sweden once had a high rate of sex crimes. Authorities reasoned ignorance of the opposite sex was a major contributing factor and, starting with the younger generation, began to integrate all aspects of life in a more-or-less unisex environment. Any "mystery" of the opposite sex evaporated and the rate of sex crimes in the country began to plummet. Meanwhile, our own segment of self-righteous right-wingers attempt to keep us mired in ignorance, prudism, false modesty, and related "values," which, hilariously, they often do not practice and adhere to themselves.