What is the purpose of carrying out / performing / making / doing / conducting a risk assessment

"If you think your organisation might be affected by a terrorist attack, you should carry out a risk assessment and apply appropriate protective security measures. A risk assessment will help you decide on the threats you might be facing and their likelihood. "
http://www.cpni.gov.uk/securityplanning/risk.aspx

"How do you do a risk assessment?
Assessments should be done by a competent team of individuals who have a good working knowledge of the workplace."
http://www.ccohs.ca/oshanswers/hsprograms/risk_assessment.ht...

"Why perform a risk assessment?
It is the equipment manufacturers responsibility to assess the users specifications and to ensure that the usage of the equipment, considering its capacity and limits within the work environment, and the maintenance program, will satisfy the users requirements."
http://www.industrialsafetyintegration.com/risk-assessment-f...

"The OECD Guidelines for the Security of Information Systems and Networks state that all organisations who develop, own, provide, manage service and use information systems and networks should conduct risk assessments in order to ..."
http://www.enisa.europa.eu/Pages/ENISA_Working_Group_on_Risk...

"Who can Perform a Risk Assessment?
Only a person certified by the Department of Community Health as a Risk Assessor can conduct a Risk Assessment."
http://www.co.livingston.mi.us/health/environhealth/aq/pdfs/...