The resolution of an A4 piece of paper is a crisp 3508px x 2480px. For comparison, my MacBook Air is about a third of that at 1440px x 900px.
And, the processes companies have developed over years are tailored to that medium. While tech has gotten drastically cheaper in recent years, it still needs to get cheaper still for most businesses.
I spoke about this recently at NYC.rb. https://news.ycombinator.com/item?id=13446715