Ask HN: When to build a voice interface in a product

When should one build a voice interface in a product? I am listing use case areas below, can you please suggest more:

1. When visual interface is not an option or not an easy option. For example - When driving car, I would like to interact through Google Maps through voice.

2. Searching/clicking multiple times can be replaced by asking a pointed question with voice. E.g. Asking question to a voice assistant. But user can type as well. Why have voice interface here?