Isn't that the point of a pager system?
Idea being if you're woken up at 4am because of a flaky test or some issue you'll be more inclined to fix it. And if it's a recurring issue, you'll really want to get it sorted or else your life will be hell. It also pushes emphasis on serious testing methodology and the idea that Amazon is a 24/7 business.
It actually makes a fair amount of sense, but it's also brutal and contributes to burnout and attrition. I also think this is starting to change for some teams.
The team I was on (retail-related, not AWS), shifted away from the rolling schedule with your counterparts in India taking over for the other 12 hours in order to push the "promote ownership" BS.
The only problem? Management was constantly pushing for new things to get done on extremely tight deadlines (including "emergency features" that needed to be done and in prod in days when they likely required a week of design efforts to get right, never mind actual dev time) so you have two options:
(1) Develop something stable, with good test coverage and the like, and work to fix it if it breaks... and work 20 hours to get it done.
(2) Shit something out as fast as you can and hope it breaks when someone else is on call (who likely will be too busy triaging SEV3-5's during business hours to even think about spending time fixing the root cause of the SEV1/2, rather than mitigating it and moving on...or, even worse (!) (/s) try to get the actual feature owners to fix it) in order to maintain some semblance of work-life balance.
I'll leave it as an exercise to the reader to guess at which route was generally taken.