No, you're wrong there - book authors also have multiple nicks, and course vendors often try and get away with having three or more nicks. And then there are those who use their Profile to suggest they are, say, in different parts of the world when they're not.
I find that it's not what they do, but WHY they do it - and I would say that in 99% of cases it is because somewhere along the line they are a vendor.