hashing filenames in webpack - why?

I came across the following in the webpack docs:

   {
    output: {
        path: path.join(__dirname, "assets", "[hash]"),
        publicPath: "assets/[hash]/",
        filename: "output.[hash].bundle.js",
        chunkFilename: "[id].[hash].bundle.js"
    }
}

What is the point/purpose of adding the hash to file names? The docs talk alot about how to do it, but not why. What are the scenarios in which this is beneficial?