I believe the "historical" example of why this is important is found in the way in which the ancient river civilizations were "good" and "happy," until said rivers didn't provide for all the people who depended upon them to survive. What I'm linking to is actually a serious, Big War for the Future, kind of post.. Consider this a tiny slice, but still, one you should pay attention to. It's a response by an industry professional, for whom I'll vouch as an expert, and who doesn't blog, because it's not yet worthy of attention, from the professional perspective:

Clarification: Fairfax County isn't dumping classics. Here's a statement from the Fairfax County library director: "Recent media reports have misled readers to believe that we’ve eliminated all copies of classic titles from our branches. This could not be further from the truth...Because there’s a growing demand for more and more books in more and more formats, we have to balance the need to offer classic literature, and satisfy public demand, with the physical limitations of our finite shelf space...Therefore we have to make difficult decisions about what items to keep in our collection." In fact, many of the authors cited in the Washington Post's article, "Hello, Grisham -- So Long, Hemingway?", like, um, Hemingway, are not being discarded.

Motive: Circulation, or how many books are checked out, is a library's most important statistic. State and local funding for a library is determined based on circulation, and it is one of the primary success metrics used to determine the efficacy of a library's programs or leaders. If a library isn't moving materials, they don't get the public's money, which seems like a fair bargain.

Reality: Public libraries have always had to had to balance cost vs. access. They still help any patron get the right information, in the right format, for free or low cost. For example, Fairfax provides free, online access to jillions of magazine articles, research reports, and reference databases. They offer Interlibrary Loan, and even a chat-based reference service. Fairfax, and 4,000 other public libraries across the country lets you download--for free-- audio books, eBooks, videos, and albums. Your own public library probably offers all of these services, too. Question is, when was the last time you entered your public library's website or branch?

Sad Reality: The answer is probably, not for a long time. Use statistics show that library patrons are very much senior citizens, the poor, and families with young kids, and that as the economy slows, library use increases proportionately. The tradeoffs being made by Fairfax, and most other public libraries are just indicators of how America is changing. Demographic and economic change means less space for 3rd-string classics to make room for more English as a second language materials,large-print books, DVDs, free Internet terminals, or removing shelving all together to make way for an expanded Children's story room.

Amazing Fact: You can still get anything in print, or out of it, from your library, online or on paper. Seriously. Call your PL's reference desk and ask a real person for help with virtually any information request. It's so cool!
However, for all of you young, affluent, no-kid having, broadband at home persons with plenty of leisure time who visit the library to pick up a classic because you happened to be nearby or needed to use the bathroom--the public library is doing its best for you, but there are other services that are getting a bigger piece of a shrinking library budget pie.

Disclosure: I am a librarian.

There are so many issues raised here. It may be an ugly, "1996" cliche to speak of them now, but now is when those once ideological and fashion oriented motifs have finally come to the public fore. Which means, ahem, the whole public is (or should be) participating in them. Add your thoughts, intertubes people. I'll get to my own later.