I find this really interesting, and am amazed that more sites and services don't surface some of their analytics data to users. Look at the success of yearly "wrap up" campaigns (disclosure: I work for a company with one of the most famous versions of that mechanic, but don't work on it).
You'll get users opting into some data and tracking if there's some tangible benefit to them on the other end. It seems like people love learning about their usage of products, and there's a lot of data that people would be happy to share if they got some benefit too.
For example, I know Google tracks when I click a link in a SERP - but now that they surface the "you've visited this X times, last time on Y", I'd happily opt into that data collection because of the pseudo-utility/interest factor of it.
The one that seems most natural is that organizations don't want people to know how much data they have on them. If too much of it was customer-facing and not wrapped up in a cool "2019 Wrap Up" video, then pressure would mount to be even more transparent, and eventually accountable for, the data organizations collect.
I think there are a few others, like the value to the bottom line that it offers. Most companies optimize heavily there so the only real applications are the ones that would like to drive more revenue, such as "Only 2 seats left!" or "Last One In Stock!" messaging based on urgency and fear. One-dimensional stuff.
I also look at it from the resources perspective. I think lots of companies are spending time and resources pretty poorly. Companies I've worked with outside of startups often forget how and why they make money and end up spending lots of resources on things that might not matter. Service professionals, for example, usually rely on a network connection like the local Chamber of Commerce for business. Despite 80%+ of business coming through that channel, they insist of trying social media or PPC ads instead of doubling down or identifying a similar network when they explore growth. This is natural ignorance that they can learn to overcome.
I really hope we get more data-sourced initiatives in the future. I use a few apps that do a little bit of it but leave a lot to be desired: Goodreads, Strava, Nike Run Club, Spotify, Audible, Kindle, & YouTube come to mind.
My dream is to have a Life Dashboard. I had designed it with some of these apps in mind but the API's and the output I'd get weren't enough to pursue when life got busy.
But I would hate to start seeing "You, personally, have visited this site 14 times" start cropping up because it would remind me how much information on me is available. Intellectually I know this data exists in Google Analytics, but actually seeing it would creep me out.