So many good answers here!
I'll add one more: attending high school sports. Used to be, teachers sat at the door, took your money and handed you a ticket -- in you go. The hardest part was having cash money on hand. Now it's all electronic. You have to purchase a ticket ahead of time and show the teacher at the door your smart phone ticket. Don't have a ticket yet? We'll point you to a QR code on a poster over on the side wall -- you can go purchase a ticket. What's the problem? Grandparents who just want to see their kid play basketball, but they don't understand apps, etc. And people who don't have a credit card.
One more thing I don't think anyone's mentioned: convenience fees (which none of us find even remotely convenient) for buying online. I don't mind the fees when it's a choice, but when your ONLY option is to use their service, I despise it.