The Kindle's great for when you're out of the house and can't just browse the bookshelf, but I do love a second-hand bookshop and still enjoy printed books. Also, presentation can suffer on screen, especially when compared to a full-colour illustrated paper book. Kindle does allow you to find specific books and get them almost immediately, and many of the classics are available free.
It's the same with music; if you go to a shop looking for a specific record, they probably won't have it. On the other hand, if you're just browsing to see what you find, a shop is better than a website.
There are also still many titles that are not available as eBooks yet.