Those who do not use a bug-tracking system tend to rely on shared lists, email, spreadsheets and/or Post-It notes to monitor the status of defects. This procedure is usually error-prone and tends to cause those bugs judged least significant by developers to be dropped or ignored.
Integrated defect-tracking systems make sure that nothing gets swept under the carpet; they provide a method of creating, storing, arranging and processing defect reports and enhancement requests.