Reasons behind why average fish only live for 3 weeks after sold

People also won goldfish from fair. I think they should stop giving out live animals as prize. Goldfish is one of the worst thing you can have as a prize, because it takes time to prepare a tank to receive a fish. These prize fish mostly die because the winners often don't even have a fish tank to begin with, and many of them don't have the necessary knowledge for keeping fish when they won the fish. Nor there is any time to prepare the fish tank to receive fish safely even if you know what you are doing. Unless you have existing well established fish tanks.