The easiest way is to use the $3 "spec-grade" receptacles which come in a box instead of loose in a bin. Guess what happens when you touch it? Ouch! By having a ground path, you give the electrical current somewhere else to go (instead of through your body. Electrical grounding is a fundamental safety mechanism that provides a low-resistance route for fault current to return to the source and trip a circuit breaker or fuse. Specifically, grounding ethernet cables serves. Is it OK not to connect the ground wire? It is entirely possible for an electrical device to not use the ground. Especially for low-power devices, such as routers, mobile phone chargers, small lamps, and so on. If there's been a wiring update since, it's possible.