Why are mattress toppers smaller than the bed like a queen bed is 60x80 and the mattress topper is 57x77?

I inquired about this directly to a manufacturer, and they said that the store that I bought the topper from Wal-mart) requested that size, specifically, and they gave in to their request so the store would sell their product. It's a matter of selling something cheaper. If you want the full-size, look for it, and expect to pay a little more for it. I did and it was worth it for me. Not worth it for the first store - I returned the item - they lost out on that one.