Picard and later Janeway were always shown doing their recreational reading with print books, rather than on a pad.
Because they like the feel of it. A PADD feels like work - they use them so often. Paper books have acquired the connotation of relaxation, the way soft, loose-fitting clothing feels more cozy than stiff starched uniforms.
Even with the data pads, Seven of Nine is shown on two separate occasions giving Naomi, then Icheb several pads; one for each subject, instead of it all being on one pad. Again, not all that many years before the inventions of the Kindle and Ipads.
Storing files on individual devices is technological redundancy - if you lose one to a corrupt file/wipe, you don't lose them all.
And there's that funny scene where Bashir and his genetically modified superfriends wrote up a bunch of scientific studies, and Bashir starts handing them all to Sisko. One study per padd, until Sisko is holding like ten Padds in his hands.
Knowing their brainpower, just imagine how long those reports were. Maybe they needed one PADD data storage amount per report.