why its important to run first linter

Question

I saw in many webpack.conf.js examples that people run in the loaders before all the linter and would like to know why is that so important and if it's a must to use? If so, is there anything that maybe will be better to use then the eslint-loader?

Here is an example:

 module: {
    strictExportPresence: true,
    rules: [
      // TODO: Disable require.ensure as it's not a standard language feature.
      // We are waiting for https://github.com/facebookincubator/create-react-app/issues/2176.
      // { parser: { requireEnsure: false } },

      // First, run the linter.
      // It's important to do this before Babel processes the JS.
      {
        test: /\.(js|jsx|mjs)$/,
        enforce: 'pre',
        use: [
          {
            options: {
              formatter: eslintFormatter,
              eslintPath: require.resolve('eslint'),

            },
            loader: require.resolve('eslint-loader'),
          },
        ],
        include: paths.appSrc,
      },