Like the video industry, where the tape must get into Blockbuster. In the physical world you need middlemen to transport, store and display goods. The Web gets rid of people who do this physical collecting. Think one-stop shopping. Think quality control.
Editors weed out the trash.
Of course, the best Web middlemen do both. You know you will not only find lots of content. But also that it will be of a certain quality. Which you use to attract the top content providers. Prodigy doesn't have the eyeballs.