This is to make it clear that every user registered with a game is also obliged to keep his login data for this account in such a way that he does not forget it. If a user has begun to submit to the Quest + screenshots but then notes: "Crap I forgot my login data, what do?", Then this task for him after the expiration of the time, lapsed.
In short: Forget your login data, since you were to blame if you can not submit screenshots and thus finish the tasks.
Addition: If you try to falsify the screenshots, you can calculate with a return of the screenshot and a warning to block your account.