If a country like Argentina (or Spain, in the world's championships) goes and takes the gold medal after having beaten the USA, they want it to be a fair and square victory. Nobody wants to say "we took gold because we beat the USA's B team".

And of course there are some teams in the Olympics that will never even approach beating the USA, much like swimming, athletics etc. contestants that have results that are minutes behind the winner when the top athletes are separated by mere hundredths. That's the price of having Olympics that actually allow every nation to send at least competitors, even when they don't have any athletes who actually stand a snowball's chance in hell. And if you get trounced painfully by a vastly superior opponent, well, at least you've had the experience of competing against him/her, which you ordinarily wouldn't have, as a lesser god from some less prominent sporting country.