Voice interfaces are not the be all and end all of communication. Even between humans we prefer text a lot of the time.
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.
And there are people that unfortunately cannot speak.
Fortunately, there are solutions.
I want to add that I think you are missing my argument here. Devices that allow you to speak without speaking shall soon be available to us [0].
The important aspect of my position is to think about the relevance of "applications" and "programs" in the age of AI, and, as an exaggeration of what is shown in that post, I was wondering if in the end, UI is not bound to disappear.