What is the point of a sack lunch - if any at all?

I have my adult Sims eat right before work but during active jobs, they always get hungry throughout the work day. This is especially annoying at the hospital, because they magically buy things from the vending machine from across the hospital, wasting time and money. I thought packing them a sack lunch would be a good solution, but they spoil SO fast. It says 8 hours when I make it, but it always seem to spoil much faster.