Working in paint, you deal with a lot of different folks. The "I don't cares", the contractors, the "HGTV wannabes", the "I kinda know what I'm doing homeowners" and then we have the fickle people who don't know what they want. Most paint places usually don't take paint back unless something went wrong on our side. I once had a lady who tried bringing back a purple and got mad when I told her I couldn't turn it gray. She also couldn't comprehend why we would take a loss from her stupidity. It's like a birthday cake, odds are you'll never find anyone who wants the same thing as you.
Then you have the people who don't pick up their paint. Regardless of what happens, we always tint our "oops" paint a different color to prevent someone playing "the game". White or near-whites are always super easy to turn a different way. Darker colors like black and browns, those are much harder to turn, so we usually have a "wait period" before we put it on the rack.