This on-call scheduling is a desperate attempt to cut payroll to the absolute minimum. They want the people there if they have customers, but they don't want to pay them if the customers don't show.
Of course, it is also a reaction to absenteeism and sick calls.
I had a restaurant job with an on-call person. The on-call had a greater responsibility to be available than the person who was actually scheduled. I was on-call on a day for a family reunion. They called, and I was unavailable. I got fired.
If the .01 percent weren't so damn greedy (and the roughly 40 percent so damn shiftless) maybe there'd be a break for the folks who actually want to work. 2 Thessalonians 3:10
I'm so allergic to bosses, I can't even do warranty work.