An acceptable use policy (AUP) is a document that defines the rules and guidelines for using an organization' s IT resources, such as networks, devices, and software. It aims to protect the organization's assets, security, and productivity. An AUP should be formally acknowledged by users to ensure that they are aware of their responsibilities and obligations when using the IT resources. Without formal acknowledgment, users may not be held accountable for violating the AUP or may claim ignorance of the policy. This can expose the organization to legal, regulatory, reputational, or operational risks. Lack of data for measuring compliance, violation of industry standards, and noncompliance with documentation requirements are also possible risks from not having users acknowledge the AUP, but they are less significant than lack of user accountability.
References: Workable: Acceptable use policy template, Wikipedia: Acceptable use policy