You're right, it doesn't need to be an average. Meteorologists are interested in outdoor air temperature in the shade, away from local disturbances like buildings and the ground. That way it's not influenced by uninteresting local effects like the color of the walls, direct solar heating (affected by the properties of the thermometer itself) or somebody turning the oven on.

That 70.7 degrees from the satellite was ground temperature, not air temperature, so it can't be compared.