It's just like anything else that we used to live without ... mobile phones, call waiting, microwaves, you name it. Doesn't mean that having new things today isn't an improvement or more convenient in some ways.

I've used printed boarding passes sometimes and other times used the app. Using the app isn't necessarily more convenient when it comes to the boarding pass, but the Delta app can quickly tell me if my flight is delayed, gives me gate updates, and alerts me when my baggage has been loaded onto the plane. Could I get along without it? Sure. But is having that information on my phone useful? Of course.