Comment by phkahler

A lot of the complexity here is because the gear selector is considered a safety-critical part. They may also consider LED indicators on it as safety-critical information to the driver. Those two things - is the transmission receiving the real intent of the driver, and is the driver being told the actual state of the system - are just the top level. Security is also starting to be a concern, though I think there is room for debate about how far they need to go with that. It's common to have all drivetrain components on a dedicated CAN bus with a gateway between it and other stuff. Your infotainment system is not going to put the car in Park regardless of what you run on it.