Why is it impossible to shop as a guest?

A lot of online vendors offer the opportunity to order goods as a guest, i.e. without registration.

The items listed on handball-uebungen.de usually are available in ebook format (PDF, mobi, ePub) and will be unlocked in the user’s personal download area after payment. You can access the purchased items via this download area at any time (for example, in the gym). As delivery will be made via the personal download area, users have to register prior to the purchase.