As VAMarine said above, IDPA makes more sense for defensive-oriented shooters, but to keep it useful, you've got to use your normal carry rig. Sometimes folks get tired of losing by just a few points/seconds, and decide to go to a different (faster) holster for the matches. Next thing you know, they're far away from their preferred mode of carry, and then it becomes just another shooting game/sport. If you can "keep it real", it can be useful as well as fun.
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)