This story is from an indian company, the on-call "expectations" might be different in your country. We were responsible for a 400k RPM service. It handled ads, so it was fairly important to the business. Whenever I had to go out for a night, or go out for a family event, or whatever, I was always able to hand over on-call to a team member for that duration. Of course, this also happened during other's on call, where I would take over. In fact, this happened daily! From ~7pm to ~9pm every day I would play football or whatever. I would always hand over on-call to another team member during this time. I usually wake up earlier than others, so I used to respond to alerts during those hours regardless of who was on call. The nights where I was staying up to watch champions league football matches or some other reason, I would take on-call as well. We just set up pagerduty's escalation order appropriately. Probably helped that there were just 5 of us in the team - easy coordination. Of course, this was my first job, and I messed up quite a bit, but I noticed the others following a similar system without me as well.

It also depends on the nature of the alerts I suppose. For us, the majority of the alerts could be checked and resolved from a mobile phone (they are alerts that could strictly speaking be resolved in an automated fashion, but the automation would get complex enough with dependencies on other service's metrics that we wouldn't be sure of not having bugs in _that_ code). About once a week or two weeks we would get an alert that needs us to look at the logs and so on.