There's data that is used to improve the experience and software itself (UX).
There's data that is used for market segmentation and advertising (Marketing) by the company who creates the product, often including psychological data from UX (1.) as well.
There might be data based on 1. and 2. that is sold off to partners or used for external advertising if a business is based on that business model (like FB)
I think it's worrying that companies are in a position where institutions on the outside can tap into it and misuse it for their means, taking advantage of those artificial echo chambers that are created to help market segmentation and advertising in first place. They would need to change their business model, because the tight control and bubblification makes the high conversion rates businesses take advantage of possible in first place.
I think this business model sucks for users, because your UX suffers, forcing you to optimize for marketing and segmentation purposes instead experience, to compete with other platforms with similar objectives and audiences. People who care about their experience will just use something else in consequence.