Wallets are usually small and fit in pockets, unlike bags which are larger. His new wallet is so compact, it's perfect for the front pocket of his jeans.
Pro Tip 2/3
Casual Accessory
A wallet is a personal item and is often a casual accessory, less formal than a briefcase. He took out his wallet to pay for the ice cream at the park.
Pro Tip 3/3
Privacy Concern
Discussing the contents of one's wallet can be seen as invasive or rude. It's impolite to ask someone how much cash they have in their wallet.