The popularity or the lack thereof has nothing to do with AI. AI writes good Haskell code, certainly not worse than much more popular languages like Python.

But I just don’t think terseness matters much; most of the cost is spent on reasoning tokens, not the sheer volume of code output.

One "did not compile, fix error, try again" loop takes so many tokens, that a well-trained-on lang like JS/Py/Bash/C easily outperforms a strict one.

The benefits of strict are still the same: once the code grows bigger you have alll kinds of guarantees built into the software, that JS/Py/Bash/C needs lots of test achieve the same.

Since writing code is cheap, it like to go more on the tests and the strong typing, simply because it is so cheap. Why write Ruby/Py/JS when you can write Haskell/Kotlin/Rust? There's simply no reason not to be doing TDD these days.