I guess this this is more a question of what constitutes "good enough".
If I am a teacher in class and I want to grab a quick scan that is still of reasonable quality to show to the students, scanner pro does the job pretty well, and way better than snapping a photo and emailing it to yourself. After that, the benefits of using a dedicated scanner just seems very marginal compared to the extra effort required. And some teachers use a scanner, only to set PPI to 200, meaning the final product is all grainy and pixellated, meaning my iPad still churns out better quality scans at the end of the day.