To be fair, self-driving cars don't need to be perfect 0 casualty modes of transportation, they just need to be better than human drivers. Since car crashes kill 2 million people each year (and maim another 2 or 3), this is a low bar to clear...

Of course, the actual answer is that rail and cycling infrastructure are much more efficient than cars in any moderately dense region. But that would mean funding boring regular companies focused on providing a product or service for adequate profit, instead of exciting AI web3 high tech unicorn startups.