Imagine if, as you walk along a street in downtown the small shops, which depend on advertising (right?) have these little boards outside their shops with some advertising. Actually this is pretty normal in most places.
That is a bad analogy. You are comparing apples and oranges. The website publishes content you consume for "free" (paid for by ads) where as a store front is trying to get you to buy a product (you pay for what you consume).
Now image that you go into a bookstore and read an entire book while there and then you walk out. How long before that book store closes?