I shoot to the best of my ability if I can help it regardless of whether it's registered or a regular comp, if it weren't fun why would anyone do it ? Maybe peoples perceptions of fun is different, the adrenaline rush with individual demanding targets, the rush of not dropping easy targets, the "high" of a decent finish, the dismembering of each stand with friends afterwards, the flashbacks to misses or better still, hard won straights, to me these are all fun.
I agree some (usually the better shots) appear not to enjoy the process but I bet even they're having more fun than when they're sat at home or doing anything else.
ps. I do know one or two who are just so constantly sour faced you wonder why they do it.