It’s not about typing faster. Effectively the difference of speed between qwerty, dvorak, colemak, etc. Are significant but not very big.

It’s about avoiding repetitive strain injuries. If you type all day long for a living, something like carpal tunnel syndrome can destroy your career. Did you know that Emacs pinky is actually a type of injury. Anyways, keyboards are the number one source of RSI in office workers. Alternative keyboard layouts reduce fatigue and strain to hand ligaments by reducing the need for repeated awkward finger motions.

If you actually wanted to type as fast as people speak, you need something like a chorded steno keyboard. If you think you can type fast on qwerty, you have never seen a stenographer doing their thing.