The reason why functional languages doesn't take off is because programming languages are tools, not an end in themselves. Carpenters that are obsessed with perfecting their power tools would rightly be out of a job in a very short amount of time. Furthermore most of these "perfections" aren't even virtuous - in the sense of searching for improvement - but just self-indulgence and aesthetics.
Functional languages are dense, hard to read, have a high cognitive load, and are thus unproductive beyond the proverbial garage startup. They are also designed and used mostly by mentioned power tool decorators rather than practitioners, with the inevitable end result.