number one reason is quicker discovery of content. It is a hint to the Search engines of importance, but not a guarantee.
Sitemaps will help search engines scan and index your content easier. But indexed content is not the same as having good rankings. For good rankings you will need to write quality and keyword rich articles, and you will need to work on getting inbound links from relevant high quality sites with relevant keyword-rich anchor text.
Hi, XML site map and html site map gives easy access to search engine crawler. It is not giving your website top ranking in any search engine. If you would like to get top ranking in search engine, follow search engine guidelines and increase link popularity with anchor text link popularity.................and watch your website ranking with that keyword............it will be much better..........close to your dreams.
The main aim of submitting a sitemap is to make sure google will know about each page in your website that he might will not discover otherwise and index it. Besides , nothing much.
site map is very import for a web sites because search engine's crawlers some time crawl very few pages of a web sites. IN site map we mention all about our sites. when crawler crawl this page that time crawler get all information about site and than after crawler crawl the hole site...
Agree with the above in that it aids the crawlers to get your new content indexed quicker. Definately worth doing as it only takes a few minutes to set up.