"if the government decides that no one can spend over $100 to heat and cool their house every year it will automatically happen??"
Obviously the government can't control your thermostat direclty, but they can enforce minimum codes that are for societies good. Like minimum insulation which reduces how much you indirectly use the thermostat.
Ever watch those earth quakes in third world countries where all the buildings are rubble. Then watch a news report from a Government that enforces structural codes and see how much better off the people are?
Sure that house was a lot more expensive because the governement required deep footers and tie downs, etc, but I'm betting when it saves you life you wont' be complaining.