I think its more: Comparing multiple companies, my total yearly income won't be any higher if I pick a company that requires oncall than if I pick one that doesn't, even if the one that requires it compensate for it. I can do the same job at company X for 200k without being on call, 175k at another that requires it, or vice versa...there's no correlation.
So if its not obviously worth my time, I just wont' do it.
This sounds particular to your experience. There are definitely companies where on-call time is compensated.