Hurricane season and electrical outages will still exist in 15 years and paper has proved to be the only storage medium that doesn't change every 20 years.
Hurricane season and electrical outages won't wipe out your Amazon library (stored in the cloud), while a hurricane might wipe out your paper library. Also, it might actually be easier to find a 30 year old book on Amazon than a paper version.
On the other hand, Amazon going bankrupt will wipe out your cloud library.
BTW, 20 years ago was 1994, and PDF was initially released in 1993.
