system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5 why aren't trains automated?
gpt
In the event that something goes wrong, you want a human on board who knows how to operate the train. Since it's quite challenging to get someone onto a moving train after the problem has occurred, the company running the train needs someone onboard at all times. You want that person alert and not sleeping on the job, so you give that person something to do at all times that keeps the train running.

Since you already have someone onboard that needs something to do, you might as well have that person driving the train.