There are several reasons.
Mostly for the wonderful convenience of it – I have hundreds of books on my Kindle.
They’re all right on hand whenever I want to refer to them.
No stacking more books onto overful bookshelves.
Ebooks are so much cheaper.
I love trees as much as books.
It’s for this last reason I was interested to read a piece on the environmental impact of print versus epublications. E-Readers Vs. Print Books (via CustomMade)
It looks at both sides of the equation, so if you've ever wondered about which is more eco-friendly, here’s the link -