Brick-and-mortar bookstores offer a spontaneity of browsing and purchasing that online just can't match. Browsing online is possible - I do it all the time, and have quite a wishlist on Amazon for the books I want "later" - but it's just different. Links at Amazon will tend to keep you in the same genre, so you have to make an effort to jump to another category. Strolling moving through a bookstore, though, will let you wander effortlessly through categories.
We don't have a Barnes and Noble in my city - the only one in the state is on the other side of it from me - but I'm aware of six bookstores in town, three of which are exclusively used books. I love used bookstores, and try to buy at least one item every time I visit. I don't want them to go away, so I try to support them. My support has left me with an estimated three-year backlog of unread books.
I have a Nook, too, with a lot of public domain novels on it, but I don't use it as much as I thought I would. I also have an iPad, with e-reader apps, but I don't use that for book reading much, either. Rather, I use it mostly for web browsing.