It's too costly to ship the item back. For small items this is a no brainer, and for very large items as well. There's a sweet spot where the return cost not so

It's too costly to ship the item back. For small items this is a no brainer, and for very large items as well. There's a sweet spot where the return cost not so high as to kill the profit and the item can still be resold - packaged electronics come to mind.