This is useful for say a Doctors Appointment were you know you are going back to see them, but do not the time and date because it could be subject to some test you have to take, or in my case to renew prescription for pills you are taking for an incurable condition like diabetes. I realize you can remove the date, but then you lose the history of when you last appointment was.

Why complete it all, then? Why not just clear the due date field?

@dbsk Keeping track of completed tasks, for one.