There are many reasons why we have decided to stop charging overdue fines, but the main one is that overdue fines are widely recognized by professional library organizations as a form of social inequity. The American Library Association and others have conducted multiple studies that show that imposing fines neither teaches responsibility nor motivates borrowers to return items on time. Instead, assessing fees makes patrons less likely to return to the library. It also keeps people from using the library in the first place if they fear being responsible for a fine they cannot pay.
The bottom line is that we want library services to be as equitable and accessible as possible, and removing overdue fines is the best step we can take as an organization towards that goal.