The door leaves evidence

In any venue the same conversation turns up sooner or later: somebody claims their ticket was never scanned, or that nobody told them about a cancellation. Without a record, that argument is won or lost by whoever insists harder.

Door scans and the emails that go out to the customer — refund, cancellation — are stored with their timestamp. It is not a feature you put on a poster; it is the one that stops a twenty-euro argument turning into a one-star review.