Require more IO, add complexity to any wiring harnesses, make repair or replacement more difficult.

None of those: In modern cars you just plug those things into the CAN bus. One connector.

Why do you think every other car isn’t made this way if it comes down to cost?

Most cars don’t have seat adjustment motors. And as to others that have that functionality being able to operate it continuously: [citation needed]. Remember these are off the shelf German car supply parts, you’ll find the exact same hardware in, say, a BMW.