Thanks for reminding me of one of the funniest things I have ever seen involving a cop. I had a friend who was a police officer. Short, rotund, and weighted down with umpteen pounds of gear. Feature this man running down the middle of the street, holding his equipment belt, and watching a tall, athletic, young man fade into the distance.
He did not appreciate me standing just outside the store where I worked, laughing my a$$ off at him. He also did not appreciate me stopping him from harassing two of my customers who were also observing his Keystone Kops episode.
I've asked the same question you asked in your post. I've never gotten a coherent answer, other than, "It's necessary."