Doctors, firemen and cops are obvious examples, but I've called plumbers at 2am because of a burst pipe flooding the basement. I've called locksmiths well past closing time due to lockout. I've called landlords at all hours for apartment emergencies. Society needs on-callers of all kinds. It's not surprising that some people are vociferously against holding the pager, and I sincerely wish those people success in avoiding it. But someone will always have to step up and they should be appropriately rewarded for it (I've been on-call and was considered lucky to have gotten overtime for it, which I think is strange because it's just a well-aligned incentive structure that any smart company should have)