eBooks have several well-known advantages, but for all their worth and utility, there are some areas in which they just cannot match real books.
To name but one: multi-sensory input. Humans are designed to experience the world around them with as many senses as possible. Physical books can stimulate up to four of our five senses. Sight (obviously), hearing (the rustling of pages), touch (the feel of paper, the relative thickness of the part of the book you've already read vs. what is still unread) and (especially on older books) smell.
eBooks only really offer sight, and, to a very limited extent, touch. That this paucity of sensuous input does not satisfy us as much as a physical book should not come as a surprise.