Why Aren't All Cables Pre-Burned In?

Most folks don't buy enough cables to justify their own cable burner. Yet, many cables take 2-4 weeks to burn in. This makes it very difficult to compare cables (did I just answer my own question?). Why don't manufacturers burn them in so you can tell what they sound like when you unwrap them and plug them in? Does the burn-in go bad after they sit on the shelf for a while? If so, wouldn't the second burn-in be quicker when you brought the cables home? I don't get it. Help! Thanks in advance. Hey, maybe some cable companies are out there listening.