The customers buy from Istock, shutterstock so on....I dont' think they care for the name...and yes, there are some freaky nicknames out there.
Some people use nicknames because they don't want people to know they produce work that can be had for a few bucks or cents, while they are doing custom work for their own clients and charging a decent amount of money...They would rather have their real name associated with the latter.
Other people want to be known by their microstock work, or don't care about using their own real name.