The screen is required for the FMVSS standard mandating rear view cameras. The jump in part price from that to touch is less than the amount saved by not having to tool up all the knobs and buttons, paying someone to run wires for all of them, paying someone to assemble all of the fiddly bits, and paying someone to install them in addition to the cost of already installing the screen that would eliminate all the other cost if it were the only input.
The screen is required for the FMVSS standard mandating rear view cameras. The jump in part price from that to touch is less than the amount saved by not having to tool up all the knobs and buttons, paying someone to run wires for all of them, paying someone to assemble all of the fiddly bits, and paying someone to install them in addition to the cost of already installing the screen that would eliminate all the other cost if it were the only input.