Building with one bus is just easier. It's not some nefarious end goal.
It's like putting everything over IP (VoIP, video over IP, audio over IP, etc.) and then just running Ethernet throughout your building. From an engineering perspective, it's just way easier. Routing wires -- on a circuit board, in a building, in a car, in anything -- is just a real PITA.
Now it's definitely true that having to flash something on the CAN bus to make it work is possibly due to greed, but the original idea of putting things on one bus is not.
It's like putting everything over IP (VoIP, video over IP, audio over IP, etc.) and then just running Ethernet throughout your building. From an engineering perspective, it's just way easier. Routing wires -- on a circuit board, in a building, in a car, in anything -- is just a real PITA.
Now it's definitely true that having to flash something on the CAN bus to make it work is possibly due to greed, but the original idea of putting things on one bus is not.