A small screen isn't going to ruin the otherwise luxury experience of a Hyundai or Kia.
Automotive screens sizes are small because they must exceed vibration and temperature tolerances of other devices, which drives up cost. Unlike an iPad, in-car screens need to work from ~0F to ~130F every day, because the back-up camera MUST work.
When Tesla introduced giant screens, then ran into problems with panels not being "automotive grade."
A large screen with bad UI design would feel cheaper.
With physical buttons and knobs, you can have finishes and smooth tactile feedbacks that make them feel luxurious. However with touchscreen UIs it is extremely hard to make it feel polished and high-quality, almost perfectly balancing efficiency and aesthetics, like apple used to do.