If your absence would break the company, then they need to be compensating you accordingly and have a backup plan.

I've worked heavily in the upper eschelons of BOH for nearly two decades now. I set very very clear boundaries. There are emergency protocols should shit break while i'm on leave.

Congress is one of the worst possible examples. They could easily delegate their vote on days off if that were allowed.

He did not, in fact, get elected. He is a Green Party candidate and he typically comes in 3rd right behind the Republican in the primaries, or has his last few losses.

There's also a real limit to how many staff a given schedule can support. You don't hire people that don't have any work that they're needed to perform.

Put yourself in the shoes of that example person. You were hired but as long as everyone else is healthy and functional, you're always superfluous. Your hours will be cut repeatedly to avoid wasting labor costs, but you'll still be expected to be available. If you're instead on call, you will be expected to be available for all days you agreed to be on call for - you can't work a different job or get wrapped up in personal things that you can't set down or pause.

There's a difference between a full staff and a skeleton crew staff. But in both cases, a sudden unplanned absence like illness or injury will require someone to work extra hours or the business will have to do without that person. A fully staffed property, like a hotel for example, might have two desk agents that typically work together for the same shift to ensure customers never have to wait too long for service. The job can be done with just one person, at cost of customer experience, and that's what you'll see from places running a skeleton crew.

What you won't see, however, is there being a third staff member who is there purely to cover for one of the other two. That's already handled by the supervisor (if one exists) or manager.