Verisimilitude
Was it really over? The war, that is.
Harry did not believe so.
Why didn't Harry believe the war was over? The seven horcruxes were defeated. He killed Voldemort. Well, technically Voldemort killed himself – backfiring curses, what an annoyance. Harry had also died and was resurrected in the process. So why didn't he think that the war, the war that had lasted decades, was not over?
Harry would not answer that question.
Although, if you really wanted to know why. Why don't you ask the lovely, green snake that Harry was just conversing with?
One shot – or not...?