If you want to keep the individual commits rather than squash the into a single commit. This is useful if the author of the PR actually wrote good commits that you don't want to make into a single commit. I'm also thinking of the case where a squash could turn a series of commits into a single commit with a massive amount of changes that is harder to grok when going back historically.
So the company who owns the rights to it can make a nice chunk of change off new book purchases (especially the purchases made by the buzz from the movie).
I have been waiting to see this company die and I hope the end is near. They may try and save it with virtual currency gambling as their next con on the human brain but it is inevitable.