Also you really don't need to subscribe to all of them. Who needs that much content? I can't even keep up with my Netflix or YouTube queue, let alone the others. I have Amazon Prime, but never use it. HBO for a couple shows, but could subscribe only during their seasons.
With streaming, we can avoid this because it's possible offer packages:
Price X includes ads
Price X+Y has no ads
As long as Y is something enough consumers are willing to pay, you can always price yourself out of the ad-watching category by paying more. The trouble with out conventional "freebie" internet services as we know them is there aren't enough people willing to pay the additional Y.
It is just a small step from this kind of self-promotion to showing ads for stuff on Amazon. After all, they have my purchasing and article browsing profile and could easily try to find articles that I might be inclined to buy. I would put some bucks on the line betting that we will see something like that in the next 5 years.