Audiobooks have a very small number of accents. Often they’re recorded by middle-aged, or older men with a standard accent. (Think newscasters, and most actors)

One of the advantages of CommonVoice is that breadth of voices. By having more, and different types of voices, you can build a more robust system, which works for more people.

For instance, my wife is a nonnative English speaker, and had trouble for years using Siri. Alexa can’t understand small children. And of course, elevators can’t understand Scottish accents. https://m.youtube.com/watch?v=NMS2VnDveP8