You can only read or stare at a screen so much. If you have a four hour layover and then a five hour flight it's nice to be able to save the reading for the plane. Plus, it's healthy to walk around the terminal, not just sit since sitting is what you'll be doing on the plane. Some airports are almost fun to be stuck in, others are just torture.
Perhaps the airports should provide free treadmills, exercise bikes, weights, etc. (and showers). Airports would also be an ideal venue for rotating museum exhibits. Line the walls with secure glass-windowed display cases, and invite the thousands of little special interest museums around the country to participate through some central coordinating office that keeps the displays rotating. It is possible to walk without shopping or stopping in at restaurants to eat. McDonald's-type play areas for kids would be good too.