Book scanning is essentially a variation of format shifting, and debate about the legality of format shifting has been going on for as long as modern digital technologies have existed. For better or worse, it is definitely a grey area, and definitely subject to variation between jurisdictions. Large scale rightsholders have been doing some unpleasant things to try to defend their profits against the push to legitimise/legalise format shifting in Europe, for example.
Scanning books almost certainly is not copyright infringement.
At least in the US, you are overstating the certainty. While I agree with you that it should not be infringement, prior to this ruling, the legal status of scanning books you own for personal use was not clear.
The qualified expert opinion I got regarding personal scanning was from a law school professor specializing in copyright (and who actually participated this case), and was along the lines of "it's probably legal but there is not yet settled case law".
This ruling probably moves it closer to settled, but I'd be suggest against placing large bets unless your qualifications exceed hers.
They exist, but are well aware of the risks. And sometimes they find it wise not to test the legal boundaries:
Any book you cannot scan?
Unfortunately, WE CANNOT SCAN ANY PUBLICATION BY McGraw
Hill. They do not allow us to scan their publications. When
we receive any publication by McGraw Hill from customers,
we will return it back by charging actual postage fee."