Prolog is not just about defining grammars. It's a full logical system that lets implement "reasoning" tasks easily. Nothing prevents using it when one faces such challenges and connect it to the rest of the application written in a more appropriate language.
You're right, most probably Prolog will not feed your kids, but knowing many languages with different root concepts (functional, oo, declarative, logical, ...) makes you a better programmer and may help to feed your kids better.
Of all the variations of Logic programming, I think only Datalog has some real use cases.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.