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Maybe because its burning hot out and people need high AC to cool down. Or the opposite in cold weather. Or to defrost windshield/rear window. Climate control is a great feature. But it's not perfect, and there are instances where you need to manually override. Just because you don't run into them doesn't mean they don't exist. EDIT: BTW on cars with physical controls all of these things are either button press or di…
So here's an example. It's over 100F outside, my car is probably 115F inside it at the moment. Setting my car to 70F inside instead of it's current 72F won't make it cool any faster. Even setting it to it's "LO" setting won't make it cool any faster. The AC compressor is either on or off. The car will set the fan speed to it's best possible speed to cool the car as fast as it can regardless of it being 72 or 70 or 68…
But more practically, if I start catching a lot of sun from the window I might want to go from 72 to 70 to compensate, even if the cabin temperature is more or less the same.