This is like a lifecycle thing. Review site startups, in their early days, view the reviewers as their customers. People want to know whether X is good or bad

This is like a lifecycle thing. Review site startups, in their early days, view the reviewers as their customers. People want to know whether X is good or bad, so come tell us! So they construct systems aimed at making sure the reviews are attractive and useful, and everyone loves them. But over time, ad revenue dries up, the new reviewer stream dries up (because most things are already reviewed), and they start looking for new revenue sources. And one such source is the producers of the reviewed products, who would love to be able to have some control over the content. And thus the downward spiral begins. We've seen this again and again and again.