I love big sites. They are like sprawling mansions in a state of renewal and dilapidation at the same time. New kitchen, old bath. Sub-zero inside, rotten wood outside.
The longer a site has been around, and the bigger that site is, the more likely it is that site will have already attracted hundreds if not thousands of links. Many of these existing links will have come about without anyone actively pursuing them. For example, I’ll bet Coca Cola’s web site has a section for employment, and I’ll bet that employment section and the pages within it are deep linked to by other sites. I’ll further bet that Coca Cola likely does not know how many other sites are linking to their employment section pages, nor have they checked.
Many large scale corporate sites have multiple content sections (AKA silos) with different personnel responsible for them. Over the years, these sites often go through several staff changes, teams, agencies, etc., and end up with an enormous amount of inbound link equity.