I can understand why some people may want to learn how to shoot these events, just to widen the scope of his/her photographic skills... But if you notice, the same people go to these events over and over. If there was anything to be learned, they would have mastered it already. If not, then it's a lost cause. Which leads me to think that they are not there to learn anything.
These people have a certain look about them. Usually, I don't notice them... but my wife pointed it out to me once, and then it became quite apparent. They have a certain geeky look about them. I say this at the risk of being flamed... but I'm just trying to describe it as accurately as I can, and the purpose is not to offend anyone.
What I think is... these people have a problem expressing themselves under normal circumstance. These events offer them an opportunity to get close to women (who are generally better looking since they are models) and take images of them. Sometimes, it gives them the opportunity to get close to them by offering to take their pictures... Without their cameras, this would have been inconceivable.
Why big guns? With big guns, they can get closer visually.
I think there is nothing bad about it. Teenages go to concerts to scream at their idols... It gives them a rush... and if they like it, who are we to say anything? It may sound a bit sad, but we are all sad in certain ways. Some of us are video game adicts... some of us smoke/drink too much... In comparison, taking pictures of women at events seems quite harmless.