I don't buy this either. If this were true you'd still see, for lack of a better term, the "redis" of Haskell. You can't argue that antirez skimped on development or that he isn't talented enough.
Where is the redis of Haskell? The ffmpeg of ML? There's something else at play here.
I think the simple answer is that a lot of problems people consider useful are intellectually not terribly interesting. Among other things, if it's been done before, the cool factor drops off a good deal.
e.g., I run a tutorial site for common lisp. One request has been for 'example of web framework'. At some point, I'll do it (it's useful), but my heart at the moment is in implementing an extensible indexing system for n-dimensional tuples. It's a good deal more esoteric and a lot more fun than screwing with http/html.
Where is the redis of Haskell? The ffmpeg of ML? There's something else at play here.