It's easy for me to forget how different my circumstances are from most other people. I'm far more likely to be in a place where I have no WiFi than a place where I have no cell service. And I don't personally know anyone outside the US, so I don't send international messages. I guess I've never paid enough attention to the fidelity of pictures I'm sent or am sending over SMS to notice a quality difference.
And then of course the vastly higher fidelity of pictures and video sent via iMessage.