Practically, many people however only start thinking about possibly needing to open some app to display it while they’re already blocking everybody else’s way at the transit gate…

The biggest practical benefit of IC cards is that they are by nature always “armed”, unlike QR codes in apps, and are readable from both sides.

On top of that, due to being able to run mutual authentication and being able to store a trusted balance, they are much more resilient to outages of any backend system. QR code tickets invariably need networking and a central backend.