1. Links ARE Usability
Foremost, links provide simple navigation between documents on a website. But in addition to regular site navigation, links dramatically increase the usability of site information since words within an article can be linked - or extended out in a tree-like manner - to many other documents of importance, like definitions, resources and items of interest, on-going, without interrupting the flow of the originating concept.
2.Links Create Direct Traffic
Clicking a link from a trusted source is one of the most popular ways for people to find a new website. If a user is on a website they trust, they are likely to follow links that it recommends - or at the least, users will follow links that make the destination site appear to provide some valuable information.
3.Links Build Search Engine Trust in Your Site
There is no doubt that link score is one of the most important factors the major search engines consider when determining where websites are ranked. The reasoning is simple: if you have many links pointing to your site from other sites, your content must contain quality, important information. A link is like a vote. Although links from important 'authority' sites carry more 'vote weight', ultimately, total 'link/vote score' is one of the heaviest algorithmic factors considered in rankings.