Well, if someone hasn't left Windows for Linux because of Lightroom even though Darktable exists there, then I doubt they're going to leave Windows for SteamOS because Darktable.
(Darktable is great, but network effects and integrations keep people in Lightroom; stuff like youtube videos, uploader plugins to gallery sites, presets, education and shared knowledge among photographers.)
Entirely possible that someone isn't aware that alternatives exist! I was not aware until recently when I took up photography again and started looking for alternatives to Adobe.
The nice bonus is that there are plenty of guides out there to teach how to migrate between Lightroom and darktable/rawtherapee. As someone who doesn't have much experience with Lightroom it was actually more difficult to learn I think because I wasn't sure how best to even edit photos, now that I have learned some basics there it was mostly figuring out how to do that in darktable.
Masks were a little bit of an interesting conundrum, and I think one of the bigger losses switching to darktable might be the lack of AI masks, if someone is dependent on those for any reason.
As a hobbyist darktable fills the need for me I think.
