To WotC: Don't forget any of the worlds! A list of nearly 100 Official WotC Worlds, Settings, or Timelines - did I miss any?

[Eltab]

There are some roleplayers who do rather Horror stuff than D&D. But Ravenloft is a thing for some of these.

This is a thing which other settings do not offer in this way.

In a similar vein, Gamma World can be used for a 'spoof' one-off adventure. I have no idea whatsoever if there would be enough player interest to turn a profit.
(But unlike Strahd, GW needs two major rules sections - psionics ("mental mutations") and high-tech - that aren't ready yet.)