system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do truck drivers in movies honk their horns by pulling on a rope above their heads? Do trucks not have the button to activate the horn inside the steering wheel like normal cars?
gpt
The air horn pull is up and out of the way so you don't activate it accidentally - air horns are loud, can get you in trouble if you blast it certain areas, certain times of days. The truck will have a regular steering wheel "meep" horn like a car, but its not much louder than a car's.   

Also, back in the day, customizing your air horn for your rig was a thing; easier to do when its not mixed up with the steering wheel electrical harness.

Plus: air horn pull = fun.