For me, functional programming and ideas that come with it, like immutability, gain relevance while constructing software for verification (making software test

For me, functional programming and ideas that come with it, like immutability, gain relevance while constructing software for verification (making software testable), as well as when trying to make software more maintainable by discouraging side-effects. For me, learning those concepts helped me write better software, even while using imperative languages.