1) I had only moved once in my life, and did not appreciate how much physical space books take up during a move. After moving ~4-5 times since going to college and graduate school, I have vowed to buy only eBooks now. Conveniently, I am also finally basically done buying academic textbooks (for which eBook versions can be scarce), having bought most of the ones I plan to use (often enough to not borrow a library copy) during my PhD and beyond.
2) In my experience, eBooks don't make it easy to annotate. Copies of my books from A Great Gatsby to Introduction to Biology are rife with pencilled in thoughts, arrows, underlines, etc. I've even enjoyed reading notes left by previous students in copies of books I've borrowed from the library (I am thinking of some comments I vehemently disagreed with in the Harvard library copy of Sartre's Search for Method, and to which I responded in turn). In that sense, library books might be more social than today's eBooks, as they can be both shared and annotated.