They often don’t want it back, especially if it is low cost and you say it is defective instead of just change of mind. They also sometimes offer you a partial refund if you don’t return it, but ask you to send it back if you want the whole amount back. I also discovered tonight that when you put in a bad review for an item it prompts you to return it, and gives you an additional chance to return an item at no cost (normally you have to do all returns in each order in one go). Which was handy, I had something that seemed ok at the start but then didn’t actually work after I used it for a while, but I thought it was too late to return it.