Exactly. I started going through the SICP book recently, not having used Lisp all that much. After several exercises I see why Lisp is useful for teaching: the syntax doesn't get in the way.

If JavaScript was used, the code wouldn't be as straightforward to write and read and you'd have to spend time going through the language's syntax for the reader (or assume the reader knows it already), all getting in the way of just teaching the algorithms themselves.