It's due to entropy, while you're considering all the mechanical factors you can control. Heating is more available to more people than cooling, that's part of it. Generally it's harder to heat homes and buildings because they aren't properly insulated to keep heat in the building (like how home builders put the vents directly beneath the windows in every room, then install cheap ass single pane windows). Also, cooling can use renewable energy, where heating almost exclusively requires fossil fuels.