Big one, because all those cars require you to touch and move the steering wheel every X seconds. All the ones that let you go hands free cost a subscription of around $500 a year (Ford BlueCruise, GM SuperCruise). And even those only let you use hands free mode on pre-mapped roads, typically only interstates.

Becasue most cars with lane follow still lose lock on the lane when the lines are hard to see (rains, snow, etc) or missing due to exists and other things.

Becasue most cars with lane follow fail to keep well when the turn gets too sharp.

Comma.ai lets you go completely hands free with no wheel nags. It also works just fine when there are no lane lines or poorly visible lines. It also supports lane change by signaling, and then nudging the wheel when it's clear to move.

There is also an experimental mode which stops and goes at stop signs and stop lights.

If the driver monitoring camera in the comma detects you fell asleep or something, it will slow the car down and pull over. All the stock lane keep that I have used in cars, if you fail to nudge the wheel they just disengage and you keep going at full speed in a straight line...

Then we delve into OpenPilot forks like SunnyPilot that let you do things like decouple gas/break control from steering control, so you can control the gas/brake yourself and let comma just always steer for you. Comma can also steer more aggressively in turns than any lane keep I have seen, and when it can't you will see the limit being reached on the little display so you know you will need to help out on that tight curve.

Experimental mode isn't the best all the time, and SunnyPilot allows hybrid mode which uses regular mode and dynamically switches to experimental mode for stop signs and stop lights.

With SunnyPilot it can even read your car's blind spot monitors to automatically make the lane change hen clear without you having to nudge the wheel.

Some have been playing with concepts of auto navigation too where the car will take exits and turn through intersections for you.

The comma.ai devices have 10W of compute power and the current driving models only use 1W, so there is room to scale to better models with teh current comma devices. There is also talk of supporting more cameras for side views and external GPUs addons with 100W compute for potential FSD level models.