Notice how you switch from "more energy efficient than most..." when talking about heating, but then switch to "is not always the most efficient..." when talking about cooling.
Both are active temperature control, and both are much more efficient than previous forms of heating and cooling.
There's also the fact that cooling uses much less energy than heating because the temperature differential is usually much less extreme. It takes less energy to go from 100F/37C > 75F/23C than it does to go from 32F/0C > 65F/18C.
There are ways to passively cool a house without airco. People have been building cool houses in hot climates for centuries. It doesn't always work, true. Once it is hot 24/7 and you don't have a source of cold anywhere you need airco. But it does explain why people consider airco a luxury item when used for cooling and not when used for heating.
I'm not saying people are always right when considering cooling a luxury while considering heating a necessity, but there is a historical reason for that mindset.
Both are active temperature control, and both are much more efficient than previous forms of heating and cooling.
There's also the fact that cooling uses much less energy than heating because the temperature differential is usually much less extreme. It takes less energy to go from 100F/37C > 75F/23C than it does to go from 32F/0C > 65F/18C.