There was only a finite amount of time they had to possibly talk. Why they were wasting their time discussing the fate of William Wood was frustrating to Hermione. She never wanted to think of that idiot again for as long as she lived. While the murder of his brother was one that still haunted her every day, she would never lose a moment's sleep over William. He got exactly what he deserved. How many times did she warn him to leave her alone? He should've listened.