Pressing the Delete button when one or more answers exist will show a warning box, "Sorry, this question has answers and cannot be deleted; flag it for moderator attention instead.".
If deleting is not allowed for a question with answer(s), why does the Delete button not automatically hide?
The questioner can use the flag button if he/she wants to get moderator attention so the delete button seems useless and might hurt server performance by wasting a round trip checking. I might be wrong. I am sorry.