I tried Googling bcrypt; one C wrapper that hasn't been updated in 3 years pops for Racket, there's at least 3 recently updated libraries for Clojure. I'd suspect the library availability is gonna be similarly tilted in Clojure's favor in most domains. Clojure has lots of compelling and new stuff - Figwheel, re-frame, Neanderthal.
What's Racket's killer library that's doing something no one else is?
I don't think anyone will claim that any JVM language or node doesn't handily best Racket in terms of sheer numbers of libraries. What Racket does have are solid core libraries with good docs.
Also, it's not a library, but the whole #lang thing seems to be the coolest game in town for implementing DSLs and other more fully featured languages.
Not an expert, but I'm guessing it could only help through increasing adoption. If Racket was blazing fast, a lot more people would consider using it and more libraries would be built and maintained.
What's Racket's killer library that's doing something no one else is?