The infrastructure was put in place for people to freely share information. The ads only came once people started spending their time online and that's where the eyeballs were.
The interstate highway system in the US wasn't build with the intent of advertising to people, it was to move people and goods around (and maybe provide a means to move around the military on the ground when needed). Once there were a lot of eyes flying down the interstate, the billboard was used to advertise to those people.
The same thing happened with the newspaper, magazines, radio, TV, and YouTube. The technology comes first and the ads come with popularity and as a means to keep it low cost. We're seeing that now with Netflix as well. I'm actually a little surprised that books don't come with ads throughout them... maybe the longevity of the medium makes ads impractical.
The interstate highway system in the US wasn't build with the intent of advertising to people, it was to move people and goods around (and maybe provide a means to move around the military on the ground when needed). Once there were a lot of eyes flying down the interstate, the billboard was used to advertise to those people.
The same thing happened with the newspaper, magazines, radio, TV, and YouTube. The technology comes first and the ads come with popularity and as a means to keep it low cost. We're seeing that now with Netflix as well. I'm actually a little surprised that books don't come with ads throughout them... maybe the longevity of the medium makes ads impractical.