I buy my meat a half cow at a time (myself and a friend split one), and you wouldn't believe the amount of ground beef that comes from one animal.

I get what you are getting at - that slaughter houses and butcher shops likely don't separate per animal. But most likely the ground beef you buy is from one maybe two different cows. Which isn't any different than when you buy four filet mignons - there's a chance they may each be from a different animal.

That's not why it's not recommended to eat pink though. When you cook a steak you are cooking the area that has been exposed to bacteria. You can't do that with ground beef because all of it has been exposed to bacteria.