Why is a sitemaps XML file important?
A sitemap is important because it enables a direct integration with the search engines. This is the fastest way to add the pages to the search engine. All mainstream search engines support the sitemap's XML protocol, example: Google, Bing, Baidu and Yandex.
A sitemap XML file is valuable to websites with changing content such as news sites and online stores. This way the fresh content will be indexed the fastest by the search engines.