Can someone please explain this me....

Why do we need 2 firetrucks, 3 police patrol cars, and 5 tow trucks all lined up blocking off 3 lanes on a highway, when the accident is just a minor bumper to bumper?

I have seen this happen way too often, a lot times when the accident is already cleared, you'd still see the last 1-2 fire trucks are still sitting across 3 lanes, you see those firefighters laughing and chatting with each other while the entire highway traffic is backed up 5 miles.

Why do they do this?