I've been screwed royally by faux sick calls. Why would I screw others with one of my own? Hell, I got a lump sum for not using them!
Screwed over royally when? When you were a courier? When you were a senior courier? When you were management?
If it's a, you weren't screwed over by the employee calling in sick, you were screwed over by your manager who didn't want to do their job and cover the sick call.
If it's b, that's the position you willingly applied for. Senior couriers sole purpose is route coverage. Don't cry when someone calls in sick and you're expected to do the job you signed up for. It's the reason you're being paid a higher paid grade.
If it's c, again, that's part of your job. Either suck it up or find a different position. Couriers don't care about your performance bonuses. Sick days are part of our compensation package and you're damn right I'm going to use them. Call me a slacker if you want, don't really care. I'm at home either being sick or enjoying my day off.
Glad you got a lump sump for not using your sick days. Up here, we get $100 if we don't use any sick days in a year. Wanna take a guess if I'm paid more than that if I call in one day?