ukrant.nl has an interesting article about the publishing industry
And that gives them far more information than you might realise. When Eiko Fried, a psychologist from the University of Leiden, asked Elsevier for his personal data in December 2021, he received an email with hundreds of thousands of data points, going back many years.
He discovered that Elsevier knew his name, his affiliations and his research. That his reviews had been registered, as well as the requests for peer review he had declined. Elsevier kept track of his IP-addresses – leading back to his home – his private telephone numbers, and the moments he logged in, which showed exactly when he worked and when he was on vacation. There were websites he visited, articles he had downloaded or just viewed online. Every click, every reference was recorded.