Pragmatically, if I was running a software house, I'd choose the language that I could get the most resource for. Resource being documentation, online sources, and most importantly: skilled developers
I don't know the stats but I suspect that lisp/functional programmers are hard to find, and, because they are hard to find, lisp is used less frequently. This is a chicken and egg situation - there's a shortage of lisp projects because there is a shortage of lisp coders (and vice versa).
I don't grok functional programming yet (I'm working on it - thanks tilly for the book suggestion), but I suspect that functional programming will always be conceptually harder (albeit more productive) than procedural. I don't know the answer, but maybe some clever companies (like Paul Graham's example) will lead the way.