>Drivers don't need to pay attention because they can't

Not at all what I said, intended, or implied. Words you've chosen to put in my mouth.

For the 3rd time: people have reaction times. It takes time for people to notice, process, and react to changes in their environments.

Never said people don't react to changes. Never said people don't see changes. Didn't even say peoples reaction times are enormously long. Just that they exist, vary, and have to be factored in.

>Emergency vehicles flip lights on and mash the throttle once they reach an intersection.

A singular extreme example amongst many far more reasonable examples, specifically to demonstrate providing 0 time for people around you to react. It doesn't happen in the real world because, as I mentioned above, you'd get t-boned for it. Obviously you have to take more care than that.