Comment by RjQoLCOSwiIKfpm

The ticket is digital-only (smartphone or smartcard), there is no paper version, and it's coupled to your personal identity (name etc.).

So some people have voiced concerns about that being used to profile the movement of Germany's citizens.

IIRC the tracking is being justified by the government "to gather statistics so we can improve the service", or something like that.

Disclaimer: I don't live there, I don't know the details.