But, again, comparatively poorly isn't really a measure is it? When the BEST performer is somewhere in the 1/3 range, it's not like there's a huge demand for it.
Look, again, I'm not trying to piddle in anyone's corn flakes here. I'm really not. But, if the best you can say about a setting is that 1/3 of people are interested in it, well... that's kind of damning with faint praise.
Or, to put it another way, if you know that a product is only interesting to 1/3 of your fanbase, are you going to invest several hundreds of thousands of dollars in it? Remember, WotC isn't interested in anything that's not going to move 100 000 units.