CarPlay (and Android Auto) are basically driving-oriented UIs that your phone pushes to the head unit in your car. This means you get a full touch screen UI with your maps and music apps of choice, plus other apps that support it.
It beats mounting your phone over an AC vent because the screen is bigger and the UI is actually designed to be safe to use while driving (fewer, bigger buttons, more use of screen edges and corners so critical functions can be activated without looking).
Car makers don’t like this, because it means users are less likely to pay subscription fees for their shittier built-in internet services.