Why doesn't Ford install these low temp. thermostats at the Factory?

I have known people to punch the thermostat out when the thermostat sticks closed. In cold weather they put stuff in front of the radiator to stop the air flow. They are not to happy when the lack of air flow toasts their engine.
Their theory is that a big peice of cardboard in front of the radiator will do the job of the thermostat.