I think that it has to do more with being a first world problem. Voice assistants are a solution searching for a problem to solve. They really have no essential application for a great deal of the world population. Being able to say "Alexa turn the lights off. Alexa, turned the volume down" hardly screams to be widely implemented or has any essential application. If we suddenly lost voice assistants right now... like a glitch takes out Siri and Alexa right now... how is your life going to be impacted? Barely... like a minor nuisance. Add that privacy concerns in exchange of something that feels like a gimmick... the technology is doomed, I believe