91% says: “public libraries are important"

I enjoy and look out for signs of my worlds colliding; e.g. This morning I first read on an SEO site (Search Engine Land) about the new PEW report on Library Services in the Digital Age. The full report and the sumary is available here: http://libraries.pewinternet.org/2013/01/22/Library-services/
Here is a key discrepancy

Fully 91% of Americans ages 16 and older say public libraries are important to their communities; …
… 31% said they know not much or nothing at all of what their libraries offer.

What does it mean that at least 22% of the population thinks that libraries are important, yet they know nothing about them? It might mean that the respondents

• said libraries are important only because of some imagined social expectation
• thought of libraries as important for others, but not for them (why would that be?
• know more about libraries than they care to admit even to themselves

Read the report (PDF) or at least its summary and you will find other statistics to ponder upon