[Skye]

Well... The Victoria Line was a form of automatic since it was made, so it seems to be more practical to have a new system created as an automatic one rather than upgrade an old system. Even with the new systems on the Underground, the driver still needs to know how to drive the train, for when things go wrong, and unlike a car, other trains can't move around a stuck train.

I guess one of the big problem with automating trains is that while it's easier to automate the normal operation of a train, there is less tolerance for any issues (a train stopping blocks all other trains on the line, there are also a LOT of people on a train at a time, stopping distance is huge, etc...).