"potentially distracting apps (email, web)" Quite on point. Few people would willingly admit to this, but a lot of research suggests that simply having option

"potentially distracting apps (email, web)" Quite on point. Few people would willingly admit to this, but a lot of research suggests that simply having options available imposes a real cognitive load. Simple additions to text like footnotes and hyperlinks produce real drops in recall/comprehension - it's not a stretch to apply this to the iPad with its notifications and rich entertainment options.