They look neat, in a useless kind of way - hj had it right. There are several things I never see labelled -- switches like these, the drawers in a mechanic's rollaround, cabinets and drawers in home kitchens and bathrooms. I'm sure there are others...
No problem for the owner, but visitors are lost. We were in a rental house in California for the weekend last week, with people sleeping all over the place after a long evening. My wife and I got up early, and sneaked into the kitchen, with her whispering "be quiet!" to me all the way. She wanted light, but she turned on the garbage disposer.