I don't know the motivation but it's a common problem for some reason. I worked at one place where it got so out of hand me a few other co-workers got fed up an

I don't know the motivation but it's a common problem for some reason. I worked at one place where it got so out of hand me a few other co-workers got fed up and spiked a bunch of our leftovers with brutally hot habanero sauce and left them in the fridge in the lunchroom. It worked.