Every one in the world on the web knows it, links are so important in the structure of web.. without links we cannot traverse from one page to another.. if you want to move from one website to another websites again the URL links is very much important. having said that Google ranking also works around this area.. where it calculate based on the incoming and outgoing links..
Even there are many factors considered for incoming and outgoing links ranking ..
If you website get the the link from high brand sites without no follow option.. that means most trusted website is vouching for you.. in that way its reputation increases.
for eg.. Google.com vouches my site by providing the links to from Google site to my site .. its lot of value and also reputation increase due this.
This gives the more trust to the user that google it self vouching my site..if incase google provides the google.com provides backlink from their site..This adds lot of value..