Because Lean 4 exists, which is a strictly (heh) better Haskell.

In seriousness, Lean is indeed a better Haskell (strict-by-default, performant data structures, BEAUTIFUL do-notation, full dependent types, etc), and you indeed do see a lot of slopped-out projects in it. However, certainly fewer than Rust, to be sure. I think the bitter truth of the matter is that additional static guarantees beyond what specifically Rust gives you -- type safety, interfaces, and linearity -- are simply not worth all that much in practical software applications.