Paper has numerous advantages over a simple digital medium (in addition to those you mentioned):
You can feel pages (a book is much more physically responsive than a tablet)
You can use pages to perform various tasks (bookmarking, etc.)
You can modify it (take notes, highlight)
Paper has cultural inertia (we have used it pretty much forever)
The digital medium can, for the most part, replicate these features and many modern e-readers provide this and more (including features like instant dictionary lookup, search and hyperlinking, which aren't possible with paper).
Despite this, many studies have findings  which show that individuals often still have a preference for paper. An interesting study on making the digital medium more competitive with paper found the digital medium lacking in these affordances :
- Tangibility: paper can be touched, moved around, "zoomed", etc.
- Annotation: as mentioned previously, you easily modify paper
- Page orientation: paper maintains its physical orientation, whereas orientation is easily lost in a digital document (this is probably why e-readers maintain the distinct page metaphor instead of merging all text into a single view)
- Multiple Displays: Paper provides an unlimited amount of "displays" because it is easy to lay anything you need out in front of you
- Sharing: as you mentioned, paper is easily sharable (just hand your book over)
- Legibility: this concern is a bit dated (see e-ink paper and high contrast displays), but this study found that digital displays were harder to read than paper
: Ruth Wilson. 2002. The "look and feel" of an ebook: considerations in interface design. In Proceedings of the 2002 ACM symposium on Applied computing (SAC '02). ACM, New York, NY, USA, 530-534. DOI=10.1145/508791.508893 http://doi.acm.org/10.1145/508791.508893
: Bill N. Schilit, Gene Golovchinsky, and Morgan N. Price. 1998. Beyond paper: supporting active reading with free form digital ink annotations. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems (CHI '98), Clare-Marie Karat, Arnold Lund, Joëlle Coutaz, and John Karat (Eds.). ACM Press/Addison-Wesley Publishing Co., New York, NY, USA, 249-256. DOI=10.1145/274644.274680 http://dx.doi.org/10.1145/274644.274680