Once upon a time someone came up with the idea that using a web site was a good way for people to collaborate at work. Thus, SharePoint was born, and many office workers have over the years learned to love and hate SharePoint and all that comes with it.
The SharePoint team site was a place to go to collaborate and find resources related to a project, department, customer, special interest group; and the list goes on. It was the landing page for a particular context. On the front page of the site you could see documents, links to external resources and other useful information. You could even have a news feed and later Yammer embed to bring enterprise social into the fold. And this is very much what you see in present day SharePoint use as well. Dashboards and pages with contextual information en masse.