The value proposition of a physical book is that is a physical artifact with concrete ownership; you can sell it, lend it, put it on a shelf for guests to see, forget it and rediscover it a decade later, or have your grandchildren find it in your attic in 80 years.This. I have a bookcase filled with "me". Those books constitute what molded me, and (if unread) what I hoped would. My longevity being in some doubt, my kids being very young, and my ability to tell them what's in my head limited, in large part I keep that bookcase filled and arranged in hopes that someday they will discover it, read the contents, and so absorb much of what their father is (or, at that future date, was).
E-books, while convenient, can be lost en masse in an instant. Heck, a bunch vanished last week from my tablet when I upgraded the operating system (most were recovered, but not all). My wife may be irritated at the space occupied by my paper books, yet therein is the point: they're not going away any time soon without real effort. Atoms persist; bits are fleeting.