Haskell is suitable for, and designed for, bleeding edge experiments, not for practical usage. Its low popularity says very little about the "market penetration" of better engineered functional languages.
There is no other popular functional language either. Except if you count imperative languages which let you, optionally, write functional code, except that in practice most code is imperative.
> Haskell is suitable for, and designed for, bleeding edge experiments, not for practical usage
The notion of practicality depends on what one wishes to practice. You, for instance, are practicing FUD spreading, it's practical for you to say these things without actually doing work with the tools provided.
I tried to learn Haskell, and while the language has merits every library I attempted to use was a problem: at best not documented enough, but more often a half-baked proof of concept.