It's still correct regarding ebooks and audio files, you're not paying for the files but the rights to keep a copy of the file and use it personally.
If the files are not protected by DRM, then there's no technical limitation on copying or redistributing the file, but according to your license agreement you're not permitted to do so.
In practice, no one is probably going to come after you for copying your music files or ebooks across your devices or sharing it with friends, but you don't own the file. Try mass distributing it or reselling it long enough and you'll attract someone's attention.
If it becomes possible for users to access the product without also driving ad revenue, they will soon discover that the service they offer to users is just as much a part of the core product you describe as the ad platform. Without eyeballs, ads are worthless.
Then there are two choices:
1. make people pay for that service directly (i.e. acknowledge as a product, separate from the ad business); or
2. make the part of the product with ads good enough and palatable enough thast users keep visiting.
* Sell you a physical product
* Sell you a service
* Sell information about you: your conversations, your clicks, your friends, etc
* Sell you ads
Smart TV's are an example of all four at once.