Although I don't know what it's like to be a doctor, I imagine that if I was one, I'd often find myself saying, "I can see why you think that, but that's not how it works."
The body can be a confusing beast, so it's definitely possible for seemingly logical conclusions about it to be flat-out wrong. For instance, although our veins appear blue, that doesn't mean the blood moving through them is.
A similar "close, but no cigar" trend has existed in the bodybuilding community for years and there just happens to be an entire market that can fulfill its demands.