Your ears have some enormously valuable properties. They are located just inches from your mouth, so they can understand your utterances far better than smart speakers across the room. Unlike your eyes, your ears are at work even when you are asleep, and they are our ultimate multi-taskers. Thousands die every year trying to text while they drive, but most people have no problem driving safely while talking or dictating messages–even if music is playing and children are chatting in the background.
Source: Burrows, P. (2018). The future is ear: Why “hearables are finally tech’s next big thing.
Audio is going to be the next important user interface for human-computer interaction. You could argue that it already is (see Google Home and Assistant, Alexa, Siri, and Cortana). If you think of it as a bandwidth problem you can see that we can take in so much more information by listening, compared to reading. And, unlike reading, listening frees us up to do other things at the same time.