How did this start? I don't know. Why don't they keep their wallet in their front pocket? I don't know. Is this useful in any way? I don't know. Basically, I don't know.
Here's what I do know. Obviously guys don't carry around purses, so can't carry the wallets in there like girls do. (Although some girls have been known to carry their wallets in their back pockets, as guys do). Girls have bigger wallets usually. Won't fit in back pocket. It's ridiculous to even think about wearing a wallet in a front pocket. Preposterous. Back pocket wallet imprints are cool. Front pocket wallet imprints are downright embarrassing. Back pocket is easy access -- both for owner and thief.
And here's the kicker. Why guys should not carry their wallets in their back pockets. When guys sit down, depending on the thickness of the wallet, their butt is uneven. Over many many years of sitting with an uneven butt like that, the spine gets crooked. And once that happens you're screwed. Can't walk properly anymore, can't play hockey anymore....screwed I tell you. And that is why guys should not carry their wallets in their back pocket. But of course they will. As will I. Because carrying it in the front is plain ridiculous.