There's also just completely failing to account for callouts in planning, which I saw a lot of when I was a manufacturing supervisor. Upper management breathes down operations' neck to only have people doing the most high cost function they're being paid for as much of the time as possible. If someone has been trained to run a line, they don't want to see them doing 5S upkeep or sweeping, they want them running that line the whole shift. Unfortunately, this extends from the most senior positions down to the new hires, so they schedule the fewest people for each role they possibly could safely operate with when they come up with their production plan. Quite predictably, with humans not being robots, this throws the whole thing into chaos the moment one person calls out. Upper management gets into a tizzy about schedule attainment numbers while demanding to know how this could possibly happen, only to sit down with planning and pull the same bullshit with the following week's schedule.

If you have a couple of redundancies in your scheduling, you can just postpone lower priority tasks and roll with it. If everyone shows up, you can have people work on stuff like training, preventative maintenance, house keeping, and a million other things.

For reasons apparently only getting an MBA will lower your IQ enough to seem reasonable, upper management in manufacturing loves doing those skeleton crews where a single absence means mandatory OT and 6-7 dry work weeks to try and salvage what can be of the production schedule, while demanding to know why we struggle to get and maintain staff for these roles.