Not to defend op, just answering this question: code clarity, readability, simplicity, correctness, clearer error handling, ...... Depending on how much faster

Not to defend op, just answering this question: code clarity, readability, simplicity, correctness, clearer error handling, ...... Depending on how much faster is "fast", these things can (dare I say, should) trump efficiency. Essentially this is about optimisation vs premature optimisation. That's a horse dead for decades now.