In theory you are right about IDPA being practice for self defense and to some extent, it does that. But in actuality it is a shooting competition with rules. Quite a few rules and if you regularly go to a competition you will hear people complain about these rules as being unrealistic.
So rule: you must shoot from behind cover and take the targets tactically. However the Course of Fire (CoF) description may alter this in some way.
Rule: you must not drop a magazine on the ground unless it's empty or you had to yank it out because of a jam.
These two are reasonable, but let's continue.
Rule: You have to reload behind cover and when doing so, you can only move one foot (pivot foot). This is true even if you are behind a 10 ft barricade, shooting from one side and then moving to the other side. You can't reload while moving.
Rule: You may shoot out in the open if the CoF description tells you to. However, if you run dry while moving, you can reload while moving to cover, but once you reload you cannot shoot until you reach cover, even if it means not shooting some targets.
The reloading while not moving is a new rule. I've never heard an explanation why it's that way. In the real world I would reload on the move and then continue shooting if that was my only choice.
So, as zincwarrior said, it's a game. It certainly is practice in terms of being able to shoot, but it doesn't train you for being shot at.
Boondocker, I wasn't offended. I have a small frame and even with an XD 9mm subcompact the butt shows if I only wear a shirt over it. In the winter I just wear a jacket, but in the summer it's just too warm and would look even more suspicious if I wore a jacket. I'm retired, so I dress casually. I figure that non-gun people will have no idea and if a bad guy did realize it he just might leave me alone.