[pjmlp]

It is called legacy.

For several reasons, the hardware required to run Lisp code was too expensive vs what was required to run C, Pascal, Algol and their descendants.

Business don't change programming languages, just because. Unless you are doing greefield projects, there is a whole eco-system from tooling, building, trainings, developers, legacy code that needs to be taken into consideration.

By the time computers were getting cheap enough to handle FP at reasonable price, the OOP finally managed to get into the industry at the enterprise level. As such it got the place that could have been taken by FP.

OOP goes back to Simula and Smalltalk, which happen to also be Lisp inspired.

As for not producing results, many train schedule systems run on Lisp.

http://www.siscog.pt/