I am a little offended, because our main playroom is in the basement, but it is a cute way to get parents attention, hahaha.
We spend time both upstairs and down, as well as heading outside at least once a day. I can see why someone would not love having their kids in a damp, dark cellar-type space. But if the lighting is good, the floor and ambient air is a comfortable temperature, and the room(s) is/are set up properly; who cares?