Some do, I’d be surprised if it’s most. And e. coli isn’t only introduced to beef at the point of it being ground, beef can have e. coli on it before it’s ever ground. With cuts of beef, when you cook it any part of the beef that was ever exposed to the world is seared at temperatures that will kill e. coli, but since beef is ground raw and then cooked that level of protection is no longer there.
Like I said–I eat medium rare burgers, I just think people need to recognize it is inherently impossible to guarantee ground beef doesn’t have e. coli in it, unless you literally tested every serving you put in your mouth in a lab first.
Rare for me, just warm through the middle. Hard to find anymore, but I had a fantastic rare burger at The Counter in Miami Airport last month.
Pork is best cooked medium and it doesn’t taste good rare. The history of trichinosis in pork has made it very difficult to overcome this notion but it’s simply not an issue anymore. Pork tastes better at medium rare than well done, in my opinion.
Fish? You have heard of sushi, I presume? And shellfish? There are probably some venomous fish that should be cooked to a certain temperature, but raw or seared is preferable for many kinds of fish.