Web content is rarely very dynamic. With the exception of social networks and news sites, most websites would be largely indistinguishable from what they look like now if they were serving the same page as yesterday or a week ago. Technologically we could trade the 'rendered on request' model with the very latest data for a 'rendered and then cached across the internet for a day' distributed model very easily.

Psychologically however, no one would agree to it. People believe their content has to be available to everyone the instant they press Publish.