Emojis in real life are just tone, facial expressions and body language. Natural language is feature rich, you just overlooked key aspects in which smilies and/or emojis are attempting to replicate.
And Google Assistant is not going to be using facial expressions or body language as input any time soon. I mean, it could, but I'm not sure how people would appreciate their phone saying "you look mad, would you like smooth jazz?" or "you are pacing and seem to be anxious, may I recommend breathing exercises?"
I can't wait for the day I have a "What's wrong?" "Nothing" "Something seems wrong, what is it?" "Nothing!" fight with my phone and computer. Progress indeed.