They definitely make automated reasoning about code easier. But perhaps they don't always make it easier for humans. See for yourself by comparing functional an

They definitely make automated reasoning about code easier. But perhaps they don't always make it easier for humans. See for yourself by comparing functional and non-functional versions of various algorithms on this site: https://rosettacode.org/wiki/Sorting_algorithms/Merge_sort https://rosettacode.org/wiki/Sorting_algorithms/Merge_sort