Why shoot a match?

Well, since you asked...
I corresponded with a gentleman over another blog's comment section about the usefulness of shooting action-pistol matches. He disputed my take on their value, suggesting that one wouldn't learn much from IDPA or USPSA or ICORE or steel to take to a gunfight. Here was my response:

You should note that I never mentioned improving combat efficiency, not for newbies and not for masters and pros.
What I pointed to was gunhandling.
I officiate a lot at all kinds of matches, and put on a lot of them, too, and I'd have to say I've never been accused of being a "rulz lawyer" or anything of the sort, so I'd ask a bit of slack, there.
Here's what I know from running many hundreds of shooters through this varied match situations: shooters who haven't been through serious, organized competition that works with a structure descended from the IPSC rulebook are much, much more likely to be deficient as gun handlers. Not always, just much more likely. That's not an Internet thing; that's from actually being on the range with literally hundreds and hundreds of shooters in thousands of runs.
Gun handling starts with the four rules but really comes down to three things: muzzle discipline, finger discipline, and establishing a safe condition and location for ALL of the parts of the shooting situation.
We have police competitions, too, and I've run hundreds of police officers in match stages and can tell you, ISPC-type range officers frequently dread having LEOs on the firing line, even veterans, even specially-trained ones. Without dissing law-enforcement training, since one of my very best friends is both LEO and a high-level, thousand-buck-a-day LEO weapons trainer, the gunhandling we see is disorganized and inconsistent.
"Inconsistent" is the key. Good mechanical practices come from a foundation of consistency, which leads to reliability.
Fitting into the IPSC-plan rulebook builds a consistency of gunhandling skills better than anything else I've seen in 40 years of lead-slinging.
I'll put it the other way around: I used to think I was a damn fine gunner until the first time I attended an IPSC-derived match, a poky little IDPA match in a cornfield. I was humiliated to see that my skills as a tool operator were simply inadequate bordering on awful. And I've seen just as bad out of veteran, highly-trained SWAT guys.
There's more to guns that simply getting bullets into targets. Dealing with guns and even simply, being armed, is a whole lot wider world.
Among people who carry in public, these skills are not window-dressing or a social grace- they're vital.
A half-dozen USPSA or IDPA matches at a good club will do more to establish and solidify those skills than anything else I've seen. A large part of that is simply repetition, running through stage after stage following exactly the same, well-defined regimen.
There's always a lot of discussion about these games and their value as training devices in a tactical sense. They do indeed have a lot of value, but not necessarily as tactics. The motor skills of moving, shooting fast, and reloading are reinforced well by competing, but the biggest value of all is pressure.
Shooting in a match includes pressure and stress, be it self-contained, social, or whatever.
I submit there's no better way for the vast majority of shooters to get pressure while shooting fast and performing other tasks simultaneously. Few of us can afford professional training and the refresher training needed to keep current on skill level.
Ten or fifteen bucks a week and a box of ammunition is a cheap and good substitute for Farnam-like schooling, and may well be the best 95% of shooters could ever hope for.
With the inclusion of the rigid gunhandling skills cited above, the games have great value.
Shooters who take it further for tactical and fighting value and get specific training do better; for millions, an IDPA match is still a vast improvement in discipline and organized thinking over heading out in the back 40.
Adapting to circumstances, even if they are goofy-seeming procedural rules, is part of thinking while shooting, too. Maybe IDPA's reload-with-retention is something you'd never do in real life, but being able to still think, remember, and consider multiple elements while shooting is of enormous benefit.
You can still do an IDPA match and shoot the procedure as you see fit, ignoring the procedural penalties. You're welcome to do it, and just ignore the scoring.
All of the other value is still there. And it's still under the pressure of the timer, which many of us have trouble with enough as it is; as a stepping-stone to handling the vastly-greater pressure of a fight, it's the best most of us can ever get.
Now, one final point about rule structures. We all chafe at rules and restrictions. So do I. When it comes to shooting match procedures, if you don't like the procedure- foot fault, slide lock reload, whatever- it's just a game. You should try to get over it and move on. It won't really harm a shooter to go along with something like that for a couple of hours.
When it comes to safety issues, well, we have no idea who's coming down the driveway and so, out of necessity, usually have to go with lowest common denominator. A 180 rule or no sweeping rule might not fit into real-life fighting, but for a game on a Sunday morning, this is but a minor inconvenience and ought not to be a big mental blockade.
Meanwhile, I stand by my suggestion that for people who go armed in public, developing responsible gunhandling habits is a must, and attending local matches and accepting the regimen therein will do the great majority of shooters a world of good.
I've run a lot of people through- I've received plenty of thank-yous for my gunhandling coaching, and never had a kickback about it.
Folks know, it's important.
Hope this helps.