There are many benefits of sitemap:
1.site map gives a straight way to search engine spiders and your visitors where to find information on your site.
2.Using sitemaps has many benefits, not only easier navigation and better visibility by search engines. Sitemaps offer the opportunity to inform search engines immediately about any changes on your site.
3.Sitemaps also help in classifying your site content,that you website page as belonging to a particular category or as matching a particular keyword only because you have told them so.