One aspect that seems to be being overlooked (possibly) is the marketability of the skinning. I'm not talking about making money out of the selling of the skins themselves, more about if you are using Arduino to demonstrate a concept to a client about how something might work, then the skin of the IDE in a professional skin might be more pleasing (and subliminally selling to the client) than the standard one. It adds an air of bespoke.
I'm not bothered about them though, but I can understand why someone might want it. It's cool either way for me