There is one killer application for voice assistants: answering phone calls. I wish Siri could respond to all unknown phone numbers, screen promotional and robocalls, take notes if necessary and report what's important to me (and I need to be able to tell her what's NOT important). This is what the assistants should do, not switching lights or trying to play a random song.

Neither Siri nor its competition can do this. Speech recognition accuracy is not really important, it can just take voice notes as a fallback, or ask to "press 1" to talk to me directly.