Learned hand signals fifty years ago, and yes I remember them. If you drive a car or cycle and don't signal you are not doing your job, and not protecting your family, or others on the highway. You are letting others know what your intentions are. How would someone know if you intend to turn in front of them? Simple logic. The excuses about how stupid other people are doesn't wash. The excuse about others on cell phones and not knowing doesn't matter. Unless your middle finger is extended, no one thinks it's a bird. The signals will let others know exactly what you are going to do. There is only three of them to learn, left, right and stop. Or buy new fangled electrical ones.
Maybe we should hold ball peen hammers when we do this. That'd make people think twice before p***ing a guy that hand signals.
I think EVERYONE should use hand signals...hell most people don't use the electric ones on the cars that have them. Apparently they may be an option on Mercedes and BMW's so I've heard.
I was driving home one day and my blinkers quit blinking, so I started using hand signals. I was slowing down for a LEFT turn onto my street, arm out the window indicating as such. the guy behind me sped up and P***ED ME ON THE LEFT just as I was about to start my turn. Darn near took my arm off, and would have hit the car if I'd started my turn sooner.