You make the software button once and it's there for the many millions of cars. You have to actually manufacture and stick in the many millions of buttons otherwise. Besides the actual action was going to be software on the bus anyways. Your window switch hasn't been directly connected to a motor in decades. It's sending a "window down" message to the bus that goes to the window actuator unit that then drives the motor. You're still paying someone to make it computerized anyways, you were going to pay a team of designers to draw it up and make the plans for the physical switch as well.

The screen was going to be there anyways due to backup camera requirements and because consumers want AA/Carplay.