You really need to design the network to support driverless trains. The upgrades to support it on an existing network are almost prohibitively expensive Sydney’s “metro” line from Hills to North Sydney (and being extended to Bankstown) uses driverless trains, but the entire line was built relatively recently.

Drivers are a small proportion of the total staff anyway. There are still station staff, signalling staff, infrastructure maintenance staff, cleaners, security staff… You can’t exactly clean a train, wash down a platform, help a person in a wheelchair off a train, and so on, from home.