It still kind of blows my mind that people play it when there are far more polished options (ToME, DCSS, etc) available.
Why not to play them all?
You are creating good game - and it's the main reason. But I think that it's really important that SotW fills the niche in the roguelike world. Your game have unique set of features. Most roguelikes are only about dungeon diving, or they have very static world. You created game with procedurally generated overworld, with towns and other meaningful places. There are NPCs, some of them have quests. I don't know many roguelikes that are similar to SotW. If you want play good, plot-ful roguelike with random world, there is no other choice.