You sound like the kid in school that always asked "are we ever going to use any of this in real life?" in math class. Truth is I never needed to derive a function outside of school or college. Was learning about derivatives in high school a waste of time? I can't explain why, but I want to say no, it wasn't.

Also, many times this puzzles are useful in tech interviews to see if the candidate has good analytical skills, which is what is needed.