It's not a lisp thing. Many lisps are capable of multithreading, including implementations of Common Lisp that have had it far longer than HN has been around, and Clojure, which is extremely good at it.

It even looks like Arc, the lisp HN is written in has threads now, but Arc is built on top of Racket and uses Racket's green threads, so it only takes advantage of one CPU core. Racket does have OS threads, but Arc does not use them.