This is the emails between the YouTuber YGK3D and Anycubic, it seems like they won’t send 3D printers to reviewers who mention their GPL3 license violations.
tl;dr Anycubic uses open-source software for their firmware, but doesn’t make it public as per license agreement, and they don’t seem to be friendly to anyone who calls this out.
More info: https://www.youtube.com/post/UgkxIMpZTkXqFo0H6pDwhZpdYqMYvLhPvWA5?lc=UgxA-4LYvwrnonXuXsZ4AaABAg
Those are a fraction of a percent of reviewers. The issue predates YouTube. The days when it was only written articles was no different. They are at the mercy of not being shit listed by companies.
That is if they can’t pay for the products through the revenue of the review. Though ofc they still have to have ads or sponsors. Much more important is if they are financially stable and convicted enough not to sell out.