History also said no QB can win the Super Bowl with two different franchises. And then Payton Manning and Tom Brady did it.
And there are few coaches that even attempt to do it. Most stay with the team that they won it with as long as possible and those that leave are often at the end of their career and don't have the time to build a team again before age catches up with them. Not to mention the fact that few HCs win Super Bowls in general.
If you want to argue that McCarty is too old or the game has passed him by, that's a valid argument, but the counter is that he is the same age as Payton and younger than Andy Reid and he has a 12-5 record in 3 of the last 4 years.