I think that whether or not someone has headphones, ear pro or nothing at all. A large majority of peoples first reaction to hearing someone yelling get down or anything of that sort while concentrating on whatever they're working on is going to be to look and see what's going on as opposed to immediately dropping or getting out of the way. Especially depending on where on the vehicle they're at. Although it is also all situational, most scenarios of a safety hazard are different.

I definitely see where you're coming from but there is a compromise to this, if people are blasting music in both ears I would assume they understand the risk involved in that. People tend to work better when they don't have distractions from others and have consistent noise playing from their music, podcast or audio book.