Flashing brake lights are super annoying. Flashing lights are attention-grabing and thus distracting when you are trying to observe the whole scene and not just fixate on the vehicle in front of you.
Or if you are the type of driver that fixates on the vehicle in front of you, and a vehicle to the side has flashing brake lights, then it distracts you from the vehicle in front of you.
They should be illegal, and they already probably are illegal - in my state, if the brake pedal is pushed, the brake light must be on, and if it is flashing, then it is alternating between on and OFF. (And a judge does not care if "technically it is 1% on and not completely off" - it looks off.)
Next time you are in traffic, imagine if every vehicle in front of you had flashing lights.
Or if you are the type of driver that fixates on the vehicle in front of you, and a vehicle to the side has flashing brake lights, then it distracts you from the vehicle in front of you.
They should be illegal, and they already probably are illegal - in my state, if the brake pedal is pushed, the brake light must be on, and if it is flashing, then it is alternating between on and OFF. (And a judge does not care if "technically it is 1% on and not completely off" - it looks off.)
Next time you are in traffic, imagine if every vehicle in front of you had flashing lights.