What is the advantace of inner links

if u want your site be viewed easily by visiter , u have to arrange your site links as best as yours, why should people design site without any need, and why should people give inner links in each pages, because they let visitor access this site easily by global point of view, site is a information portal or book, visitor should find links they wanted. they get easy to have innerlinks in every pages unless they get confused. there are some links related to actual intended visitors and some links for webmasters, thats why we have to arrange these links dividing group, some important links should be displayed quickly and some less important links should be displayed in small font or in different style in far footer or where there we cant see easily.