I have several laptops and I noted that with one laptop (and only this one laptop, and no access at all with other laptops) I have access to all Springer articles (at least in mathematics) and seemingly even to all math books (such as this series of books) in the Springer website without even being logged in any account.
How is that possible?
I have access to the journals in my university computer, but even there I do not have access to the books.
When I go to a journal website like this one, I see on the right of the page "You have access to our articles". I am not logged in there (at the end of the page, above the copyright, it even says "Not logged in") or have ever tried to log in. When I click "My account" on the top right of the page, I'm told to login and thus I assume I'm not logged in in any kind of form. (I only log into Springer journal sites when submitting or checking the status of an article and then logout, but that is not via any university system that grants access).