I think it has to do with the fact that Lisps and functional programming is not something you tend to use to build a whole product on, but rather something to crack the hard nuts with at a higher level of abstraction.
For example, at Chartboost our backend runs on a LAMP stack, but our new implementation of the smart ad targeting algorithm involves using Clojure (another Lisp dialect). Chartboost is definitely not "Made in Clojure," but I think it's fair to say that that doesn't mean that the language isn't being used to build a useful product.
I strongly disagree that Functional programming is something that inherently is not suited to building a whole product on. Although I cannot providing evidence that it always is the case, Jane Street is a wonderful example of what happens when a bunch of really smart people get together and use a statically typed functional language to produce a robust piece of software which solves hard problems. Not everything at Jane Street is written in ML, but MANY of the employees write in ML, the software devs, the quants, te systems folks, and even the traders.
For example, at Chartboost our backend runs on a LAMP stack, but our new implementation of the smart ad targeting algorithm involves using Clojure (another Lisp dialect). Chartboost is definitely not "Made in Clojure," but I think it's fair to say that that doesn't mean that the language isn't being used to build a useful product.