Say you got inside a datacenter, or nuclear power plant, and pulled a cable from a control unit, you would probably be able to control stuff too, and probably more sensitive stuff then the room lights. As soon as you get access to stuff you are not meant to access, it gets exponentially hard to protect from privilege escalation.

As a security exercise, assume a malicious hacker have physical access to your LAN. (shares, KVM, IPMI, MITM)