[Drakim]

For the same reason Siri and Ok Google isn't just a long menu of 500 options.

Having a tone dial menu works as long as there are only a few places to route you, and as long as all situations only have a handful of answers.

Furthermore, you can have tricks like looking for keywords in your human speech to make sure the guy you get patched to has the expertise to help you. If you say "my router won't turn on" you won't be sent to a password reset monkey.

At least, that's the theory.