I agree with your sentiment but when someone comes along with the smart idea of running a knife between the business end of the OS and the driver stack we end up with abominations like UEFI that just push the OS's duties in to the firmware.
The API of a driver is just as important as the bits they twiddle because it insidiously chains you to a particular abstraction model, i.e. a specific state machine you're building on top of hardware state. This is why Linux doesn't maintain a stable driver API. If you enforce driver API stability then you're boned down the line when it comes to moving from, say, a synchronous model to an asynchronous one.
The API of a driver is just as important as the bits they twiddle because it insidiously chains you to a particular abstraction model, i.e. a specific state machine you're building on top of hardware state. This is why Linux doesn't maintain a stable driver API. If you enforce driver API stability then you're boned down the line when it comes to moving from, say, a synchronous model to an asynchronous one.