You are the product, not the paying customer. That means you are cattle.

The farmer will build a fence to protect the cattle from predators, because it is in the interest of the farmer to preserve the cattle. But come payday, the farmer will gladly butcher the cattle for profit.

Social media users in the you-are-the-product buisness model are no different. Your user experience will be catered to you to cultivate the user base. But your experience will be actively ruined the instant it benefits the paying customer, I.e. if that means the paying customer, advertisers, will get what they want (promotion).