In my bout of insomnia, I've been thinking of what makes it a patron vs a customer. In my mind, a patron is someone that I'm giving a service to. In my particular position, I'm giving them my expertise of searching and locating specific amounts of information, from phone numbers, to books, to almost anything you can think of (except that.) A customer is someone I'm selling something to. Whether it's a service or an object, money is involved.
While it's true the library itself deals in money, overall, it's the service that's important. It's providing a service that many people (including myself) can't provide for themselves. From the free internet, computers with office programs, to free (unless they're late) book rentals, most people utilize the library at some point in their lives.
Some people claim that since 'they don't use the library, so they shouldn't have to pay for it'. I don't believe it. They might not use it - right now. What if their internet goes down? What if their child needs to write a book report? What if they lose their job and are forced to get rid of their internet? Even if they don't use it currently, chances are, they'll use it at some point in their life. Or they know somebody who does use it.
I use not one, but two libraries. The one I work my regular job at, and the one that I substitute at. I get books, movies and CDs from both of them. I use the internet. I use the programing. Mostly, though, it's the books.