Not really hard to understand, anything that allows one to customize or express their character, or something tied to their character, more will be for the most part loved and widely used, as people like to be able to make their character unique or more interesting for them at least, and possibly for those that care to show off to others.
As such even if you the OP may not care for transmog, many others do, and it is one of the most beloved features added to WoW. And anything that allows more customization, even for something minor that will not leave the one zone its for (Pocopoc) will be often used.