Sitemap is very important to rank a website. This is one of the most vital part of on page seo.
By the sitemap search engine crawl can get direction which page/post index
or not. Indexed pages/posts get priority on search engine and when
people search then it show search engine's search result. Without
sitemap on page seo is incomplete and the website/page/post never show
in search result. So it's mandatory for rank a website.
So if you don't have any sitemap and want to submit it webmaster tools then this service is for you.