I would be suspicious of any subroutine whose function couldn't at least be described in words. So I agree that a function might be practically impossible to u

I would be suspicious of any subroutine whose function couldn't at least be described in words. So I agree that a function might be practically impossible to use in any other context, but it's worrisome to me when I see a function that doesn't do something that can be described in words. In most cases, after factoring out a function from a bigger function, it's usually a good opportunity to think about what this function really does, and to make it do something conceptually simpler (even if that is less tailored to its sole use case). This way, you can even write meaningful tests for the new function.