Harry Potter and the Philosopher's Stone

Throughout most of the story, we share Harry’s point of view. We see what he sees and experience what he experiences. In the first chapter, however, we are shown Mr. Dursley’s point of view as he drives to work, sees a cat reading a map, and encounters oddly dressed people on the streets. Rowling could have given us a more straightforward third-person story without any particular point of view. Why does she choose to show us Mr. Dursley’s thoughts and reactions in this first chapter?