Eh the whole point of being on call is that you are effectively assigned to ensure that you're ready to jump on incidents quickly at off hours if needed.
I'm not sure tobacco is a good comparison here. Tobacco was a relatively easy thing to tax/restrict/ban as it serves no real purpose beyond individual enjoyment.
That's also the case at Amazon. And likely most large organizations. It's not a strict stack rank but an expectation that over a certain population size, there is a certain percentage of under-performers. It's also used as a method of calibration. Performance evaluations are hard.