Link building is the main factor why search engine optimization exists. Without links, search engine algorithms have no basis of which site or permalink has higher value and vice versa. The number of links that points to one domain is very important in increasing the site rank or page rank in search engine result pages. The more the relevant links that points to a domain, the higher are the chances that the specific domain goes up on search engine pages. However if over linking occurs, there are counters measures from various search engines to identify if the links are relevant or just nonsense.
At first, it’s not really the number of links that matter in determining the value of such page. Early search engine factors are the number of views, the density of the keywords inside a specific page, and the weight of the page and how relevant it is with the keyword used while searching. Links as a factor in search results are just made popular and are most used in search engine algorithm, that’s why links are vital and important.