Surely, it exists for some reason, but what?
The original business model was that each subject area was assigned to a specific editor, who was responsible for maintaining the content on that page. The neat thing was that the editor got a cut of the advertising income from that page, so there was an incentive to make it a good one. I don’t know if that’s how things still work.
I use it for the free knitting patterns and instructions, not available on Wiki AFAIK - but I found it via google.
As far as I know, About.com still works like Dewey Finn describes. Are you sure you don’t mean Answers.com? They do mostly mirror Wikipedia, but they also draw from several other sources, like All Movie Guide.