To which a seeing-eye dog is often employed.

Given that there is increased lack of "looking while you walk" from many people (due in part to the use of smartphones) noise from vehicles becomes a crucial indicator.

Do they really rely on car noise? Based on wind and other noise you can't be sure that you are hearing all cars.

It depends on the situation, of course, and in many cases for situational awareness, you can imagine folks want to have as much information/affordances available to them as possible. Car/traffic noise is one bit of situational awareness that is often used. Whether or not there are other affordances, losing any affordance can be a safety problem/hazard.