Idpa is a Game, it can be a fun game, it can be challenging, it will make you a better shooter,... the one thing it's not is a some what real life senerio......I have never felt the need to shoot a steel popper as I,m holding a pizza in one hand while leaning behind a conveniently placed blue barrel in real life.
On some stages a cover garment is used, there are some advantages to vests when playing the game, I,m sure that at today's outside Idpa match there was minimal use of fishing vests as a cover garment considering the weather. If the course of fire requires the cover garment you can choose to not wear something ,you will recieve a time penalty but that's ok...because it's a game. Wether you draw from appendix or 3 o'clock the concept is the same, it,s pretty much the same motion. If the rules bother you golf is also a game and if your good you can use the same ball more than once.
On another note as some one who is outside frequently I am a big fan of the vest it keeps your arms free while providing warmth.