Yeah I think it’s the money issue. The companies have more money making self driving cars. Specially since the incremental advancements make them more money on every new car sell.
While trains don’t have incremental advancements with sells associated with them. They have less training and incentives. But technology wise it is definitely easier to control speed 1D, while mostly looking at the front (maybe back) compared to the degree of control/sensors cars need.
It’s sad that I don’t know if you’re joking