Well usually it’s because of train worker union strikes and lots of lobbying on their behalf. The reality is it’s political suicide to put that many people out

Well usually it’s because of train worker union strikes and lots of lobbying on their behalf. The reality is it’s political suicide to put that many people out of work in one fell swoop and it’s expensive to replace all rolling stock in one go. So it’s down to a slow and steady war of attrition. Example: London Underground is being slowly but surely automated, while keeping an operator who is “not a driver” until they are no longer needed. And that’s one of the oldest metro train systems in the world