Not just luxury cars, even economy cars are shipping with adaptive cruise control, automatic lane-keeping, and automatic collision avoidance, and (at least the ones I've tried) work fantastically. On the highway you really don't have to do anything.
Luxury car brands ship with a limited feature set that reflects an appropriate conservatism. For example, they can detect cars in your blind spot and warn you, and they can put the brakes if someone short stops ahead of you. They have many of the required sensors but are waiting for the tech to mature
This is not true. BMW 5 and 7 series have adaptive cruise control and lane centering. I had a Tesla and now have a 5 series and the 5 series Lane centering is on par with Tesla’s autopilot. The only thing it lacks in the US is auto lane change (but it works in other countries).
Or maybe it's just the sensors being the same...