You could argue that perhaps the computer shouldn't have built in WiFi either - after all, it could tether to a phone (via a cable or Bluetooth) to use wi-fi.
Except WiFi modems are cheap because there is lots of competition and most of the patents are easy to license, so everything has WiFi now.
For me to have 4G access, I need to connect to a network, and for that I need to pay. I currently do this through my phone which I need to be connected when there is no wifi more than my laptop. Is the price of 4G access low enough to have this on my laptop in addition to my phone? Not currently.
