I think it is more about ambiguity. It is easier for a computer to intepret set tones and modulations than human speech.
Like telephone numbers being tied to specific tones. Instead of the system needing to keep track of the many languages and accents that a '6' can be spoken by.
It is also for those who grew up with the language. If I have no spellcheck, I sometimes just have to write it both ways and see which way feels 'right'.
I got both. Of it doesn't run wel on the deck, I just stream it from the PC.