Training and practice are different things. IDPA, USPSA, and 3-gun fall into the practice category. Instead of learning new skills, you're practicing what you've learned. You might learn something about your technique and equipment, but that's more of a personal discovery than formal training.
I think some people shy away from competition because they want to be more proficient before they demonstrate their skills in a public, timed and scored environment. Personally, I don't feel like I'm quite there yet, and require more time in the rifle and pistol bays, running drills. That's a nice thing about ranges that have individual pistol bays or short range rifle sight-in bays. You don't have to worry about other shooters on the firing line.
To the OP: where are you located at? Is it training you're interested in, or a place you can practice and run drills?