Just store all QR and Bar codes locally on your device.
When you leave home, you dont have to worry about forgetting a card/ticket that has a Bar or QR code on it. For example when you go the the store where you have a gift card, or a Covid certificate, or even just a parking ticket.
With the BarQR app you can even simply scan the QR code of the menu at a restaurant, and then view its content at home to make home delivery.
Note: All data is stored on the device locally and is not uploaded to the cloud.