The 10" circle is no different than shooting groups with a rifle. Shooting on paper at the range let's you know if point of aim and point of impact are the same. Like sighting in a rifle. And it's a consistent means to measure and compare the pattern. It is also a reliable way to know your choke and loads effective range. Of course you already knew this.

Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats.