Your argument is essentially against all forms of safety equipment that protect against being rear-ended, and can be used without substantial modification to argue against safety equipment of all kinds: why bother with crumple zones when I could just insist everyone else on the road were better? The reality is that I am in the car being hit, there is little to nothing I can do to make people not hit me at some point in my life (and to this date, I have been in a car rear-ended twice; in both situations the person behind us was 100% at fault under essentially any useful definition of "at fault"), and so I have a budget I am willing to spend on random safety equipment to make me less likely to be injured when this happens. I already am spending a lot of money on safety features for my car: at least these ones sound cheap to add.