For an AI to troubleshoot problems with your computer (something it's really good at today), it needs content like reddit's. Books don't and won't detail weird software issues and their workarounds. One the current training set becomes irrelevant to whatever software people are running, this is a specific area where Reddit's data is way more valuable than books.

Of course Reddit locking down access to that information leads to fewer people contributing. Reddit is dead, it's just struggling to go down.