In 2012, the Windsor Public Library in Ontario, Canada started a "no fines" program that allowed for no money paid by a patron for an overdue book. The program is prepared to end with reports of abject failure, losing the library around $200,000 in revenue. That amount also seems to be the budget for new materials for the library, effectively stagnating the collection.
Yeah. Um. Libraries are not Netflix, kids... We need that extra income. We need any bit of income we can get. In fact, the only way this possibly could have worked would be if the library's started selling ad space, effectively turning their website, newsletters and interior walls into a NASCAR racer. Hell, even if they sold ad space on all the books they check out, the could not have made back the money they lost on people being forgetful.
The biggest fault in all this is that it made libraries look bad. Look at my last sentence of the last paragraph, libraries bank on people not remembering to bring their books back. We expect patrons to get fines so much so that it is built into the budget. I have not gone in depth, but I suspect that when the library started this program they had some contingency for the money lost besides a hope and a prayer that people would circulate more.