Many of the low-speed switches are connected to a single controller that then interfaces over LIN or CAN to the car.

Reducing the copper content of cars and reducing the size of the wiring bundles that have to pass through grommets to doors, in body channels, etc. was the main driver. Offering greater interconnectedness and (eventually) reliability was a nice side effect.

It used to be a pain in the ass to get the parking lights to flash some kind of feedback for remote locking, remote start, etc. Now, it’s two signals on the CAN bus.