Magento creates a file named sitemap.xml which is used to crawl your website pages. There may be a necessity to remove some CMS pages from the sitemap.xml file in Magento 2.
Sitemaps are generated to display Google-bot about structure of your website, Magento 2 Sitemap is helping your website to crawl and indexing faster in search engine and make visible your webpages and products on google.