I would say the problem is pretty similar to why isn't Haskell more popular?

both have a different/specific (as in non-mainstream) thinking way, and it is not easy to switch from common programming languages to these. and since it isn't easy, most people don't go deeper on them

from a company point of view: if it's hard to find a good Prolog/haskell developer, then they will be more expensive, so they stick with the common Java/C/C#/Python/Ruby/JS stack