Let's just say that you create a product, it becomes really popular, then somehow someone steals that product: Would you let any user give propaganda to the "copy" product in your official communacation streams? (Propoted and supported sites ARE officialy recognized by Cipsoft).
There is also the case of TibiaBR, which people say that they left the program to talk about OTs, add advertisement on their own (when Cipsoft didn't allow it) and etc.
You can also read this statement in the fansite agreement:
"The content of the fansite has to be about Tibia only. We set high standards, therefore your fansite needs to be updated regularly. Please make sure that the information given on your website is correct and fair. The texts on your site should also be accurate concerning their grammar and spelling. We also expect you to have a professional and appealing design. If your fansite should become a promoted fansite, your content always needs to be up-to-date."
OTs ARE NOT TIBIA (The product TIBIA, even if the graphics and a lot if things are like Tibia), which supports my answer.