There would be a lot of noise pollution everywhere, with people constantly murmuring to themselves, alternated with an unresponsive silence while listening to the device‘s answer. It would seem like everybody is on the phone, all the time. Also, for me, digesting information via text is way easier, because I can jump back and forth to support short term memory - good luck with that with a voice assistant.
The iPhone (and friends) disrupted the PC because they made reading and writing mobile. Voice assistants are not iterating on this paradigm, but they are rather iterating on phone calls. I‘m skeptical that this is suitable to replace the iPhone I‘m writing this on.