As a quick reply to Skires post about the average C grader and a 30 yard target. I won't quote it all, but my thinking on that is that it's not just about the ability to shoot a 40mm disc at a given distance.
I bet your average shooter would be able to hit a 42 yard 40mm disc every time on the plinking range - put them in a competition and it's a different prospect.
Part of the reason for that is a psychological one, and that's where your 30 yard easy target helps a less experienced competition shooter by giving them a little respite from relentless hard targets.
Back to what Rob said really, less of a gimme and more of a rest.
It's mentally tiring shooting in a competition, and that's something that a newcomer has to get used to, throwing in the odd easy shot helps not only C graders but everyone by just giving them a little mental breathing space between 100+ yard lanes in a hurricane.