I think it's because it's not a hipster language, but a language for pragmatic programmers - ie. people who don't want to be forced into single programming para

I think it's because it's not a hipster language, but a language for pragmatic programmers - ie. people who don't want to be forced into single programming paradigm (like in Haskell, Closure), who want easy interaction with tons of existing JVM code/libraries (unlike in Go/Haskell), who value platform independence, who need good performance where necessary. This breed of developers (the "pragmatic" crowd) tend to focus more on just doing stuff and less on writing about it, hence less NH threads.