Search Engine Crawling: In the whole term Search engine optimization Off page optimization is a very important thing. While Google or similar search engine optimizes a page and gets a lot of links redirecting to a page it saves the data in its algorithm. This data helps to find the page/site/blog while some one is searching with that types of sites.
More Visitor: When a site have a lot of links in a lot of high page rank site/blog it automatically brings more and more visitor from those site. and it brings a lot of traffic for that site.