When you walked out of your house in the 80s or 90s, you'd have your wallet and your keys and then maybe your credit card. And then later, you have your phone. It'll be a physical wallet and a physical key and a credit card and so on. And eventually, that's all going to converge into a different kind of thing, because it's amazing that your cash and your wallet and your keys to your car and your credit card can all be thought of as a private key on your phone.