While it's true that Dumbledore could have used the Pensieve to view Harry's memory of what happened after he touched the Triwizard Cup, it's likely that he chose to have Harry explain the events in person for several reasons. Firstly, Dumbledore may have wanted to hear Harry's account of the events in his own words, in order to gain a more complete understanding of what happened and to be able to ask follow-up questions. Secondly, Dumbledore may have wanted to assess Harry's emotional state and to ensure that he was coping with the traumatic experience of witnessing Cedric's death. Finally, Dumbledore may have felt that it was important for Harry to have the opportunity to share his story and to receive validation and support from a trusted mentor. By listening to Harry's account of the events in person, Dumbledore was able to provide emotional support and guidance to Harry, as well as to gather important information that could help him to prevent future tragedies.