Well, I've come up with a guess as to why. I could be wrong, but hear me out.
Maybe the tapes are something akin to Horcruxes. Each tape contains a fragment of Rebecca's soul and if too many are destroyed, it could destroy Rebecca. That might be why the entity works so hard to protect and preserve the tapes. It doesn't want that to happen to Rebecca. Again, I could be wrong. We won't know until the next game rolls around or possibly even the next game after that. But, what do you all think? What are your thoughts?