Why not "Google Book Search" in the public library?

If my local library had the money to do it, could they do what Google proposes? Scan print books and make them searchable, but just for the sake of card holders like me? If not, why not?

Right now my library electronically catalogs and lets me search titles, authors and subjects. As is the idea for Google Book Search, they allow this so I can learn where on the shelves I can legally obtain copyrighted intellectual property that suits me. In fact, searching by subject I often arrive at a book I've never heard of and didn't know I was looking for. Just like Google Book Search. At the library this is fair somehow.

Now what if my library were to add to every catalog entry a searchable keyword? Still fair?

What if my library were to add a key paragraph to every catalog entry? Say the first paragraph of the book. Fair?

How about we make it the whole first chapter? How about the whole book?

Why not? My library paid for these books and owns these books. As a card holder I'm allowed not only to check things out but to know and search what my library contains. So I thought at least.

You know, I could make a darn lot more efficient use of my library if my library's catalog just let me search whole books, and I'm having trouble understanding why book publishers and copyright holders would wish to deny me this efficient use, not to mention how legally they might get away with it.

Aren't U.S. citizens supposed to have access to the Library of Congress too?