Virginia drivers have deplorable driving skills, and one of the things that pisses me off are drivers who do not use their turn signal.
Understanding that Notice is part of the basic principles of Contract, as well as giving Value to get Value, using a turn signal gives other drivers Notice of your intent; the other drivers get Value from knowing what you plan to do so that they can act accordingly, and the signalor (industry term) gets Value by not having the other drivers smashing into the ass end of their vehicle. Don't bother to argue with that as Contract has been well settled over thousands and thousands of years, and is way more proven than opinion.
And yes, brake lights are Notice of sorts, but they do not indicate intent. Like this morning for instance; I had no way of knowing if Incompetent Driver's BMW brake lights were an indication that there was a squirrel or other fuzzy faced creature poised precariously on the side of the road; that there was an emergency vehicle entering traffic; that the driver hit the brake pedal accidentally while scratching her overstuffed leg and will continue on or about at the same speed; or that the driver, having determined all at once that she wanted to stuff her filthy face with McDonald's latest wares, was coming to a full on stop, and had to wait to cross oncoming traffic. Without knowing that a driver is going to come to a sudden stop, it can be very easy to hit someone. That's why you're supposed to show intent.
Incompetent Driver did not give me Value, so by all means I should have blared the horn at her stupid ass, and by that I would have been giving her Value as she may have learned to use that stem thingy hanging off the steering column and avoid preventable collisions in the future. I would probably have received Value indirectly, as my children in the back seat would not have to hear me swearing nasty things, thereby parroting them in company of my wife.
I don't make it a habit to stomp on my brakes and come to a full stop every time I see brake lights. I'm not asking for y'all to come over to my house and mow my lawn; just give me some fucking Notice.