The Seattle Library has 27 locations and a million books, serving a city with 700,000+ people (and a larger metro area - I forget if you need to be a Seattle resident to get a card).
To be able to query materials across the library system, handle reservations and item transfers, and so much more these computers absolutely need to be networked.
Perhaps you meant "don't need to be connected to the Internet", but I would wager a majority of the library's patrons search the library's catalog online rather than coming in person.
In the case of digital loans, moat patrons want to download their digital books onto their personal devices - over the internet, so clearly the library services need to talk to an online service.
> I forget if you need to be a Seattle resident to get a card
Any resident of King County* can get an SPL (Seattle Public Library) card, due to a reciprocal agreement between SPL and KCLS (King County Library System).
"If you live, work, go to school or own property in King County (even outside the city of Seattle) you qualify for a free Seattle Public Library card through our reciprocal agreement with the King County Library System. (The only exceptions are the towns of Hunts Point and Yarrow Point, which are not part of the King County Library System.)".
And indeed, as already mentioned in a sibling comment, most counties have reciprocal agreements with both SPL and other counties' library systems too.
This is a more recent happening. Some years ago, you did have to be a resident of Seattle to have an SPL card. However you could still use many library services without one.
To be able to query materials across the library system, handle reservations and item transfers, and so much more these computers absolutely need to be networked.
Perhaps you meant "don't need to be connected to the Internet", but I would wager a majority of the library's patrons search the library's catalog online rather than coming in person.
In the case of digital loans, moat patrons want to download their digital books onto their personal devices - over the internet, so clearly the library services need to talk to an online service.