Investigating accidents and incidents will improve your risk management system allows you to make changes to prevent the accident from happening again.
Incidents, including near misses, can tell you a lot about how things are in reality. For example, you may have overlooked certain hazards in your risk assessment, as they have only become apparent whilst the work activity is underway.
An investigation can help you identify why the existing control measures failed and will show what improvements or additional measures are needed.