Nobody's saying it's impossible — just that like many other possible sources of revenue, such as lottery tickets, it isn't very dependable. If you're able to get 200 million pageviews a day, all sorts of avenues for making money are open to you. For most prospective businesses, though, "I will get 200 million pageviews a day and be able to maintain it practically by myself" is not a very safe assumption to make.
Not sure your point, I make my income from advertising (well company does and pays me, same thing right?) my fascination was with the single employee part.
Do not believe the hivemind here that advertising based income isn't possible.