An entry in Fortnightly Topic Challenge #35: Restricted Title 1.
Bob was mowing is lawn when he saw a white van driving around his neighborhood. Driving the van was a wiry old man. He made stops in front of people houses and took a good look at them. Then he drove out of the neighborhood. Bob was a little nervous but continued to mow his lawn. The next morning Bob had a ring at his door and by the time he got to it, all he saw was the white van driving away. He was even more unsettled at this, but tried to calm down. A few days later, Bob came to his tipping point when he saw the van driving slowly around the neighborhood again. Bob got up and called the local sheriff.
Why didn't the sheriff do anything?