This makes sense, a library is interested in keeping the books it has, not in getting profit out of users. Or at least it should be anyway

Fine free if you return the materials. Otherwise, you’re blocked from checking out materials if you hit a certain amount ($10+ usually, depends on the library). There is a likely chance that they’ll work with you to reduce it and Unless you owe hundreds of dollars, you’re probably getting your account deleted in ~5 years so that’s also a sort of forgiveness.

My library has no late fees but we do charge for lost or damaged item fees. We really just want the materials back. Fines are a PITA to deal with for both staff and patrons, more hassle than they're worth. They also can scare patrons into not bringing items back because they're worried about either the fee or being yelled at (our patrons skew young and maybe aren't used to how libraries work: they often ask about the cost for "renting" books instead of "checking out" books, and we have to explain it's a free service.)

edit: scary librarian voice. a lost item will go on your permanent record and you won't be able to graduate until you pay it off

I have cards in 3 library systems. They all work this way:

Each system requires a yearly card renewal, you have to physically go into a branch to renew, although they do have accommodations for disabilities and stuff. If you have not returned a book or have way overdue books, you will be unable to renew your card unless you return the overdue ones. The only fees I have are if I were to lose a book and it needs to be replaced.