> In driver's ed they tell you to not to use your horn when you're annoyed at other drivers

This is definitely not a cultural universal. Different countries have different practices. In some places the horn simply means “I’m here, check your mirrors”, in other places it means “You bastard!”, and in some other places it means “We are both stuck in traffic let’s make as much noise as possible to pass the time”

> only use it if there's an imminent danger to avoid a crash

Therefore the difference between the horn being readily accessible and being hidden away could be the difference between life and death.

Exactly - you need to have quick access the horn in a safety critical use case, so it shouldn't be a small button you have to find among other small buttons. You should be able to mash the center of the steering wheel.

>But you better hope it works because if it doesn't, the airbag behind it explodes.

... what? I had a car who's horn stopped working and the airbag didn't explode or go off.

In danger imminent situations you might not have the time or mental capacity to think about buttons.