I am sure that they want to prevent the public from finding out what they are getting into until it's too late. They cannot do that if all the littera-trash is available on apostate sites. Just imagine a potential call reading the Keep Yourselves in God's Tyranny book, online, when they are not allowed to see it yet, and they realize that they are going to have to give up everything. Also, imagine seeing them reading the Kingdumb Misery (I myself have a few downloaded and printed copies, and realize that they are telling me to do nothing but set up men to study the washtowel).
They really want to control information to new recruits. On the first visit, they will offer a book like the Washtowel Teach, the Showcase Washtowel, the Asleep!, and the Not Well Translated Bible. Those people are not ready for the deeper stuff about disfellowshipping, the technical rules, and that they are going to have to give up their lives--otherwise, it will turn them right off and kill the study. They also disallow people from posting transcripts from the a$$emblies, and judicial hearings, for the same reason. Plus, they do not want the authorities to see a letter to hounder-hounders only (that is to be verbally read to the hounders, and then the congregations) or the Keep Yourselves in God's Tyranny book.