From what I've observed, people have no problem talking to other people in public places. I don't see why this behavior would change for non-human listeners.

I regularly use speech-to-text transcription publicly. With my mouth close to the mic, I can speak softly enough that people outside of my personal space can't hear.

That being said, keyboards still have their place. Certainly, I use ChatGPT on my phone several times a week using keyboard input, and it's not particularly onerous.