system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did the custom of "when riding in the cab, sit in the back" get started, and why is it still tradition?

I mean besides driver safety.
gpt
It is an extension of the era when they were horse drawn carriages. The driver would be on the roof or on a seat in the front that was on the outside of the carriage and passengers would be inside it. 

It does provide protection for the driver, and it also provides privacy for the passengers and means that they do not have to talk with the driver if they do not want to. Something that you are socially obligated to do if you are sitting beside them in the front seat.