One thing to remember is that much commercially prepared ground beef is scraps and odd pieces from the rest of the meat cutting operation. It may not be the same scraps and pieces going in each time. Meat and fat are balanced to make the ratio of whatever is being prepared — 80:20, 93:7, whatever. It’s more likely closer to the real thing if it’s specifically labled by cut, like ground sirloin or ground chuck.
Also to remember that a lot of commercially prepared ground beef comes from worn out dairy cows, not prime beef cattle. And not to forget that many commercially prepared beef patties include fillers and binders.
An approach if you’re cooking at home is to pick a whole piece of meat, like a chuck roast, and ask the butcher to grind it on the spot. At least you know exactly what you are getting.
Another approach is to grind it yourself, in a grinder or a food processor. Again, you know what you got. Or you could mince it a la steak tartare — a knife or chopper in each hand and chop the meat down in to hamburger. This approach gives a nice consistency to the cooked burger.