I haven't gotten a library card in a long time, but I think you need proof of a permanent address in the same jurisdiction that funds the library, so if you're homeless, you can't use it (though homeless often use libraries to sleep and wash in, even if they can't use the actual library services).

I live centrally, in my town. The nearest library is an hour walk. The bus would be at least 30 minutes. I'd have to know beforehand that I need to reserve a computer before using it, and that spots fill up quick. I'd need to get a library card to reserve the computer, which I need to do in person. I'd need the bus schedules, and presumably my device might not be capable of accessing that or I might not be knowledgeable enough. I'd need to have cash on hand to pay the bus fare, so I'd need to find an ATM or convenience store that offers cashback.

This labyrinthian effort is basically what being a poor person is like, on a daily basis.