On a related note, car rental places now email me the contract and rental documents by default, I receive no paperwork unless I remember to ask. The problem didn't register with me right away (It was so similar to what hotels do when you travel, all paperless now) but the last time I returned the car I asked them what I was supposed to do if I was stopped for a traffic violation. "You can open the email from us on your phone and give it to the officer" they suggested. I recommend everyone ask for a printed contract instead.

As an aside, on iOS, the airline apps I have used work like the Wallet app and are visible on the lock-screen, the device must be powered on but remains locked when you display your boarding pass, etc.