This implies it's a consequential cost. Building with tactile controls would take the (already considerable) purchase price and boost that high enough to impact sales.
If tactile controls were a meaningful cost difference, then budget cars with tactile controls shouldn't be common - in any market.
It's not just cost, though. The reality is that consumers like the futuristic look, in theory (i.e., at the time of the purchase). Knobs look dated. It's the same reason why ridiculously glossy laptop screens were commonplace. They weren't cheaper to make, they just looked cool.
Not all. Knobs designed with dated designs and/or materials look dated. There's a million ways to make a knob, just use a modern or novel one.
It is the job (and in my opinion, an exciting challenge) for the UI designers to come up with a modern looking tactile design based on the principles of skeuomorphism, possibly amalgamated with the results of newer HCI research.