Facebook is still fighting with rumors that their app doesn't keep the microphone on and listen in on conversations. (Remember when people talk about something and suddenly it appears as a ad in their newsfeed?)
Without basic features like web navigation - it's really hard to recommend it vs it's competitors like the Amazon Show, or even a Chromebook.
I think it's not completely natural solution, and gives few advantages compared to a smartphone. Also not sure if people would be keen to use it in general, and especially not now after all the privacy issues and scandals with FB.