I notice odd things

This has always bothered me about movies, usually action type flicks. There is a big gun fight between people and then one person gets the drop on the other. Let's say Brad Pitt is a good guy and gets the drop on Edward Norton. Now, they have been firing at each other enough that they have both had to reload a bunch of times. This has been a very exciting gun battle. Now Pitt is standing in front of Norton, brandishing his weapon. It turns out that Norton has Pitt's family, and Pitt is threatening to kill Norton is he doesn't reveal where the wife and child are. They bicker back and forth, Norton being cool and cocky, Pitt becoming highly agitated and emotional (just like a woman...what a girly-man!). He comes to his breaking point and says "I swear on my mother's grave (this is a very emotional movie) that if you don't tell me where they are I will blow your brains all over this carpet!" (For the sake of the movie they are fighting in a very nice office with a deeply coloured mahogany desk and several paintings on the walls, which are now completely in tatters because of the grenade. Did I mention that there was a grenade? Cuz there was). To show that he is serious (and keep in mind that this gun battle probably lasted a solid ten minutes. They've each been hit at least once, a few guards (like twenty) have been caught in the crossfire, there was backflips and slides across open doorways and all sorts of excitement) Pitt aggressively cocks his gun.
I must not understand guns, because I can see no reason to cock the gun at this point. Had he flipped the safety on and now he's taking it off? If so, why? That makes no sense. Does the gun become automatically unable to fire after a minute of disuse and so he has to recock it? Does cocking it make the bullet hurt more?
I don't get it. They've spent ten minutes just pointing and pulling the trigger. There was no extra effort needed. Where did this sudden need to do something to the gun come from? And seriously, why wait to do it. If the other guy knows anything about guns, and given the fact that they were just engaged in a gun battle, don't you think he would know that the gun can't be fired yet? So why would he just stand there and wait for the Pitt to ready to the gun to be fired. Jump him, or move somewhere where getting shot isn't an option!
The movie scenario is just made up, but not the part about the gun. It happens in movies and TV shows ALL THE TIME. I used to go with it, but it has bugged me for a while. It makes absolutely no sense. I don't even think it is a very good device for making things more dramatic, or upping the tension. Ah, maybe it's just me. It doesn't really bother me in a serious way, but every time I see it happen I immediately think of it and shake my head.
If anyone knows more about guns than I do (it's be hard to know less), and has an explanation for why this might be necessary, let me know.