The idea behind libraries is that a minimum of knowledge should be accessible to everyone.

For what it's worth, there's still a lot of information you can acquire legally and for free from a library that you can't get both legally and for free from the internet.

Unless of course you're looking for information on some niche thing that nobody was talking much about after ~2000 or so.

Except sometimes you want or require a physical book... not all books on the internet are available freely, legally. Also, libraries offer free access to the internet, computers, printers, etc, which (believe it or not) not everyone can afford.

If it were true that the purpose of public libraries had been superseded by the internet then no one would be using public libraries, and they would all have closed by now due to lack of funding or public interest. That public libraries continue to exist, and that people continue to use them, suggests otherwise.

Quality and depth of information in a good library, at least for many subjects, is much greater than what you'll find for free on the internet.