This past weekend I was flying on Delta and my first flight was delayed such that I was going to miss my connecting flight, so I rebooked onto a later one. During my layover I visited the gate agent to get a boarding pass with a seat assignment.
"Do you have the Delta app?"
"Nope."
Then he pressed a few keys on his keyboard and printed out a new boarding pass for me within five seconds. I couldn't believe he was trying to kick me over to the app if it was that easy.
MLB is the exact opposite of this. You can't get tickets without the Ballpark app. No paper tickets at most stadiums. The app asks for all sorts of personal info too (which I usually spoof). They're even trying for biometric check-in now.
Aer Lingus have introduced app-only self-service bag drops, which are invariably swamped with passengers trying to get them to work while a single staff runs around clearing on-screen errors and directing people to rescan, or reweigh their bags, or move closer to the window to get a 4G signal.
Meanwhile non-app users are directed to the otherwise idle staff at the check-in desk. It's bliss.