If you trouble to take out the book and the Cessna Power Computer -- and lean properly, you do come quite close to the book figures.
I did land once with just one hour as planned in the tank and the line boy remarked that he had never put that much gas in a C-172 before.
This was a plane I had flown frequently and had verified a standard burn rate.
At a 3500' airport in the summer, you lean for best power to takeoff. Remember that you are getting considerably less than full power.