Acceptable Use Policies spell out to users what they can and cannot do with the organizations IT resources. This includes all devices and the network connection itself. It is important for organizations to have acceptable use policies as it helps protect them from various types of notices and lawsuits.
For instance, downloading of copyrighted material could lead to DMCA takedown notices, usage of certain hacking tools could be a violation of the State Law, and visiting certain kinds of websites could be against Federal Law.
Additionally, the organization can set an environment of productive and clean resource usage through its Acceptable Use Policy, and hold the right to terminate or take action against any employee who abuses company resources.