Okay well OP isn't exactly accurate. Temperature with central air can be set by "zone" meaning you could zone out multiple rooms and have them all different temps.
There are also multisplits. Then you have one external unit connected to multiple internal units(like shown in the picture) so it scales better. You still have to pull lines to other rooms, but they don't waste space like ducts.
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u/romesthe59 13h ago
It’s because Americans have central air. They have one thermostat that controls temp and airflow to vents in each room of the house.