The Case of The Empty Box/Plate of Treats

The staff of Shore Fire have a thing for sweet treats. We also like to share our treats. Most days of the week there is a plate of cookies, or donuts, or some other kind of sweet on our kitchen table. And by the end of the day, all that’s left of this plate of treats will be half of a cookie, piece of donut, etc. Why do people leave such a small bit? Why not just eat the whole thing, even if it is the last cookie/donut? Is it because you are so considerate of your co-worker who may not have had one of these treats? Or is it because if you ate the entire last treat, you would have to clean off the table, and wash the plate or throw away the empty box?