Who is digitizing the books which are rare? Isn't it even more valuable to digitize for them now that they have new buyer which can pay 100s of times more.
They're often books tied to a region, i.e. stories about a local fisherman's life and how they overcame adapting a boat to local feedstock, or the engineering that went into building the local train station. That's to say they can have little value to those outside the area but are still a rich read for locals, tourists, and those who move to the region or have a love for a place. I expect we'll see a concerted effort to organise to get these kind of book sent to regional mueseums for scanning now that people are aware they are actively being destroyed and they realise the timeline isn't how long the book can last.