Go read "Site Reliability Engineering" by Beyer et al. That's the clearest description for how on-call should work, and the way to get from Point A to Point B without burning anyone out. On-call is almost always necessaey, but should be thought of as high-deductible insurance. If you need it, use it, but just realize it's cheaper to prevent the problem than to fix it when things go wrong. And if you keep using it unnecessarily, your carrier will drop you.