1. Cooling is a lot more energy efficient than heating on average (the maximum delta needed is around 50F in the hottest areas of the US, where it gets 120F outside; for heating many places need up to 90F, sometimes more delta).
2. Places with hot climate usually cool down at night.
3. Hot climate places usually have very mild winters (e.g. here in Tucson it only goes below freezing for a few hours each year).