Voice interfaces are not the be all and end all of communication. Even between humans we prefer text a lot of the time.
Plus there are many contexts where you don't want to use your voice (public transport, night time with other people sleeping, noisy areas where a mic won't pick up your voice...).
And there are people that unfortunately cannot speak.
I cannot speculate about this, because I am not sure too observe the same.
We've had writing for only around 6000 years. It shall pass.
What GP describes sounds to me like having a friend control the computer and dictate to them what to do.
No matter how capable the friend it, it's oftentimes easier to do a task directly in a UI rather than to have to verbalize it to someone else.