It's funny, but also easy to unravel I think. Haskell sits diametrically across from the C lineage of languages that focus on practicality first and foremost. It's hard to beat practical value versus theoretical value.

I also almost mentioned that I think language extensions are one of the things that hold it back the most from being more than a research project. But deciding what set of extensions are needed to make the language practical is probably a difficult problem for anyone to solve.