The truth is it's largely psychological and has nothing to do with shooting benefits. You won't find many women shooters who are caught up in this craze.
Let me tell you a story:
Once, a man was walking along the beach and he found a Genie's lamp. He rubbed it, and out popped the Genie who granted him one wish. The man thought a moment, then replied, "I want my (penile membrane) to get longer."
"Very well," replied the Genie. "Now let me get back to my nap".
With that, the man dropped the lamp back in the sand and ran home. He fell asleep, and when he awoke he found that his (PM) had grown by 3 inches. He went to work, and at 10AM he went to the bathroom and was surprised to see that it had grown another 4 inches. By lunchtime, it was a full 14 inches longer. By quitting time, he was scarcely able to walk for fear of tripping over his (PM).
As soon as he was able, he slung his (PM) over his shoulder and ran back to the beach. He found the lamp once again, rubbed it, and the Genie popped out. He demanded another wish.
"Oh, very well" said the Genie "Now what do you want?"
"What do you think I want?" said the man, "Longer Legs!"
Now do you know why everyone is after 32" barrels?
