In the not too distant future, it may not be. Your physical wallet is on borrowed time.
Your phone, after all, increasingly provides the utility in digital form for the many reasons you schlep a Costanza-sized billfold in the first place, from showing off pictures to making mobile payments.
Think about it. At the airport, you hand your iPhone or Android handset, rather than a paper document, to the TSA agent who inspects and scans your boarding pass.
You scan your phone entering ballparks, movie theaters and concert halls, too.
Most states will accept an electronic copy of your automobile's insurance ID card during a traffic stop.
Students at Duke, University of Alabama, University of Oklahoma, Temple, Johns Hopkins and Santa Clara can or will soon be able to use the Wallet app inside iPhones as contactless student IDs. Other colleges are presumably to follow.