Librarians complain it's too hard to find good books unless they buy them from the big publishers. Libraries even hire a company called Baker & Taylor to tell them what to buy -- B&T is a distributor that's deeply connected to big publishers and won't even handle most small publisher's books. When a small publisher tries to get library sales, usually librarians say it's too much work to evaluate their books. This doesn't of course always happen -- there are ways that small publishers can sell to libraries, but it is often too costly and difficult and I know of many small publishers who've just given up on doing business with libraries. It's a disservice to readers and authors who aren't in the big publisher system, but it's how libraries do business.
Now big publishers are starting to say, libraries are in competition with them. It's ridiculous - books become popular because of word of mouth, and libraries can be very helpful in this sort of "dandelion" marketing. So hopefully more authors will wise up and look for alternative publishing approaches. And maybe libraries will start actually looking for other sources of books, but, librarians are by and large a very traditional and hide-bound lot, especially when it comes to picking books, and probably will resist changing their approach no matter how badly the big publishers treat libraries.