Because once companies get big they draw in business management that doesn't have any sensitivity to the product. That's certainly the case with Waterstone's: the books knowledge of the people who run it is relatively small. Staff aren't paid well, so turnover is high and knowledge of what they're selling falls.
Granted, running an independent bookstore surrounded by Blackwell's, Waterstone's and Foyle's (independent, but increasingly chain-ish) must be tough but I do think that criticism of the staff is unfair. The booksellers I work with - at a large bookshop in C. London, in one of the academic departments - are committed and passionate people, many of them are educated to postgraduate level, and usually are placed in a department where they can genuinely demonstrate an enthusiasm for the books.
I'm not someone for whom retail was an obvious choice of job. I'm not a big shopper by nature, but I've always loved bookshops. Every time I walk into one I feel like Orlando discovering her first book shop in London. "Send me everything of any importance!" I want to cry to the nearest bookseller. Instead, I wander the store looking for handwritten recommendations, listening to what the staff are recommending to other customers, watching other people's reading habits. I have discovered some brilliant books in unsual places. I read The Colour Purple because a woman browsing Jeanette Winterson titles was carrying it in her other hand, and it was a customer recommendation that introduced me to Mark Thomas (a few years ago, after I commented that The Men who Stare at Goats was an excellent choice). Other books that have turned out to be brilliant, I've picked up for a few pounds in bargain bookshops or as additional choices in a 3 for 2 offer. Agent Zigzag turned out to be the most thrilling book I'd read for a long time, Graham Norton's autobiography was surprisingly poignant and I even enjoyed The Devil Wears Prada. So I've become more open-minded about what I will read. I no longer dismiss military history, celebrity biography or chick-lit, bookselling has actually broadened my mind. In turn, I am a better bookseller because I'm not afraid to tell people what I've enjoyed. I've recovered from the snobbery that held me back from recommending popular titles (the extraordinary delusion that popular must mean badly-written or under-researched, there doesn't need to be any dumbing down involved in making non-fiction accessible).
I'm a bookseller because I can't live without books and I love making them available to other people. I'm a bookseller because I'm the sort of person who buys a second copy of a book I've enjoyed so I can lend one out risk-free. I'm a bookseller because I believe everyone should have access to what they enjoy reading, and because I've learned so much from the customers I've met over the years. So we're not antiquarians any more - so what? We love what we do. So next time you're in a book shop, ask for a recommendation. You may learn something...