After many years of just having basic , manual, A/C I had got in the mindset that it was only for hot weather. (and even then Mrs LV preferred opening a window. )
I agree, having climate control set all year round and just let it do its thing is the best option. It illustrates the other big advantage of A/C . In cooler weather it dehumidifies the car and clears condensation much more quickly. It minimises how often and for how long the RDMS and other safety features have to shut themselves down because ice , condensation etc around its sensors is corrupting the reliability of the signals they are receiving . Even with climate control this may take a while to clear when setting off in frosty or damp weather and can be affected at any time by dirt, squashed bugs (eg moths) or heavy rain etc. . My RDMS occasionally shuts itself down for a few minutes if signals from the side of the road are confusing and nebulous. Such as long waving grass obscuring the actual road edge.
I keep climate control on by default but will sometimes switch it off in ideal weather conditions. This does save a bit of fuel. The car will go into EV mode more readily in stop start traffic after a cold start. But having a window open also increases drag, and there therefore fuel consumption. Probably by a similar amount as having climate control active.
And A/C benefits from being used regularly all year round . Use it or lose it.
I can accept that the systems may shut down for periods if the signals are not sufficiently reliable. Better that than giving a false sense of security.
But as others may point out some car makers include duplicated and back up systems using lidar and radar sensors that are less affected by weather conditions . But these sensor types have their own limitations, and add to cost.
