Why do I also have to enter my details for « On-site payment»? 

Even with  «on site payment» it is important that the organiser can inform you if the event is cancelled or postponed. You have also concluded a purchase contract with the organiser. If you don't turn up, the organiser can charge you for the ticket. They will need your address for this.

You can find out more about data protection from Eventfrog in our blog article: Maximum data protection at Eventfrog >