Real braking happens for a reason, to avert accidents. Sane drivers don't do it just randomly in perfectly safe situations. Random braking is major risk for everyone around and if you are source of it, you are in fact danger foe others.
> Sane drivers don't do it just randomly in perfectly safe situations
You can't always assume that you will be able to tell when a situation has turned from safe to unsafe. You just can't exactly see what the driver in front of you (or the driver in front of _them_) is seeing.
And you can't assume that the driver in front of you is sane!
