[MiguelHudnandez]

Many Americans do, indeed, keep bulging tri-fold wallets in their rear pockets. And they even drive their cars and sit at their desks with them.

Often you will spot them with a month's worth of paper receipts crammed inside so the poor wallet is about to burst.

It is just conventionally where a man's wallet goes in America--One of those things where you don't apply common sense because it's just "how it is" and you've never really thought about it.