A friend of mine's first assignment as a senior engineer was to find ways to eliminate more moving parts and metal fasteners from cheaper spec products, because removing a dozen two cent screws would save the company tens of millions over the life of the design. Not just in parts, but because they're more complicated and take longer to install than just snapping and glueing a plastic shell together.

With the scale of manufacturing at companies like GM and Ford, saving a few thousand per car on parts and labor with a touchscreen infotainment system is a massive, massive amount of money. The R&D costs of converting from knobs to touchscreens would probably be covered in the first few months.