Presumably they found it more important to preserve the pages than to preserve the volume binding. The FAQ for the linear book scanner indicates that Prototype 1 mangles pages in some way (tears or folds) in about 45% of books it scans.

Moreover, it used to be common to create bound volumes by binding multiple issues of a serial together. (In some cases the bindery would crop pages to fit!) The binding is often so tight that the volume cannot open flat enough for a full scan. Separating the pages from the spine allows for the entire page to be imaged without distortion.

Edit: Incorporated correction. I had accidentally stated the claim more strongly than the FAQ supported; however, my point does not depend on the claim being as strong as the form in which I had stated it.

It sounds like that machine gets one page every 11 seconds -- maybe 360 per hour? We're getting more like 8,000 per hour.

The rule of thumb apparently is, best case, books you can't cut the binding off cost 5-8x as much to scan as books you can.

Probably because the books are far less important than the information.

That being said, they are probably throwing away an opportunity to sell the books as novelty or decorative items. But who knows, maybe the cost-benefit is just not worth it.