Also, its a lot easier to study leetcode problems than it is to study for domain-specific ones (since there are many different domains). I would expect having more domain-specific problems would limit you to a narrower range of jobs.

It all comes down to philosophy- one could argue that it's better to have interviews reflect the actual material of the work. And that such domain-specific questions would require less prep, as the candidate's experience should already be strengthening them to answer such questions. Not to mention additional career development in those skills- asking and answering Stack Overflow questions, technical blogging, side projects using the same stack, etc.

That's much worse than leetcode problems because it requires tons of work outside work. Most people, myself included, have a life and interests outside of the very narrow focus of their career, and don't want to spend 16 hours a day focused on that one aspect of life. Studying a few leetcode problems is no big deal in comparison.

Depends on the companies you're applying to, it's rarely just "a few." One of the difficulties is retention. A LeetCode a day only goes so far until you have to repeat older problems. Better to get it all done in one test.

You're assuming they will actually eliminate it though rather than just pick something else to test.

Sure, but at least that might be something more relevant to day to day work, and require less grinding than Leetcode.