The purpose of an user access review is to ensure the right people have the right access level to your business apps. The benefits for doing access reviews regularly is to avoid security breaches, avoiding overspending in licenses, and generating audit evidence to meet regulatory requirements.
Companies have to meet the requirements of regulatory standards and compliance frameworks like GDPR, ISO27001, PCI DSS and HIPAA. Regulations may require periodic access reviews to assess who have access, to which systems, and the level of access.