What do you mean by "the technology exists"? Sure, computers exist, neural networks and machine learning exist, sensors exist. Even geofenced, unprofitable operations like Waymo's exist. But that doesn't mean self-driving cars exist. And yes, of course it has to be mass market. The self-driving story would be pointless if it weren't; that's the whole reason VCs are betting billions on it.

The problem is the insane amount of training needed. The current approach of running repeated learning iterations to iron out corner cases soon runs up against the long tail of thousands and thousands of tiny, unlikely-but-possible scenarios requiring more and more data. Every time you expand the scope of the self-driving car (different roadside conditions, behaviors of pedestrians and other drivers, new roads, weather, etc.), you discover more conditions for the model to train on.

You can't just say, "my model is intelligent. Now it's just an exercise for the reader to train the model on all possible scenarios, and voila! You have a self-driving system!". You have to actually train the model to produce a self-driving car.

This is a never-ending battle. Let me point out how utterly different it is from how human drivers deal with new conditions.

No, self-driving cars don't exist. Not yet. And it's not for legal reasons.

(One technical solution to the self-driving problem would be to also modify all the roads and surroundings to reduce the number of unlikely scenarios that our models have to learn. But this kind of solution is challenging for non-software reasons, plus it would not really be "intelligent" in terms of AGI. It would be more like a tramway. It wouldn't be sexy.)