It's not really clear to me why, but lisps keep trying and keep dying. Best guess is that in the end, syntax really does matter and lisp just doesn't have enough of it.
Whether it's scheme or clojure or arc, every once in a while a new lisp comes along, and they never make it. This through decades and generations of programmers.
My (half-serious) take on this is that LISPs are too easy. A lot of little things that are hard in other languages are easier in LISP, which results in you writing the code yourself instead of pulling in a library some else wrote. This greatly reduces both the need and offering of a package manager which usually plays an important role in establishing a ecosystem and community in other languages.
In all seriousness, I think that package managers play a big role in the success of modern languages, espcially if the package managers are there from the beginning. As far as I'm aware Clojure was the only attempt at a LISP where a package manager was included from the beginning.
Whether it's scheme or clojure or arc, every once in a while a new lisp comes along, and they never make it. This through decades and generations of programmers.