If functional programming were really good...

Why isn't it used outside the academia?

I've never been to academia, yet I use Lisp.

Although Lisp isn't really a functional language - just a way to represent thing. IIRC, GCC uses Lisp internally to represent AST transformations and macros.

Any sufficiently complicated C/C++ program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Lisp.