That issue is: bandwidth. If I’m in a place / on a device that has super slow internet, I’d love to be served a very light web page so browsing is still acceptably fast. If I’m in a place / on a device that has super fast internet, by all means ratchet it up and deliver me more.
Chris Coyier wishes for media queries which could detect the bandwidth of the internet connection. This would be to cool to be true.
But even a picture tag, which could deliver different files for different screen sizes would be a step forward. Yes, there are Javascript solutions for that, but it is not perfect and it would be better if there was a simple HTML solution.