The use of the
Controller Area Network (CAN) bus in vehicles makes it possible to have multiple devices in a vehicle communicate over a single pair of wires, the same as how an Ethernet Local Area Network (LAN) or Wi-Fi LAN permits a bunch of computers to communicate over a shared medium. If a manufacturer uses a CAN bus network for controllers and controlled devices, retrofitting controls may be simpler since it only requires access to the CAN bus rather than individual control wires. (Trivia: CAN bus is used for more than vehicles, including industrial automation. The high-school level FIRST Robotics Competition makes use of the CAN bus to interconnect the robot controller (National Instruments RoboRio) with sensors and controllers.)
I have the multi-function wheel in my van, along with the pixel display in the instrument panel. I like being able to check things like tire pressure, DEF level, water temperature, fuel mileage, etc. while driving. It's particularly handy to see how outside temperature and/or driving conditions have affected the tire pressure. It also makes answering the phone or making phone calls to frequently-used numbers a lot easier. I don't use it to control the radio/music playback very often.
It would be interesting to know (intellectual curiosity) how much of that could be retro-fitted if not ordered as a factory option, but at a minimum it would require the display in the instrument panel as well as the steering wheel controls to make it work, I think.