A new employee arrives, gets shown to their desk, and within an hour their personal phone is connected to your Wi-Fi and their laptop is plugged into a spare port on the wall.
When everyone uses the same Wi-Fi network, you lose all sense of separation. Staff devices sit on the same network as printers, servers, guest phones, contractor laptops, and even random devices that were connected once and forgotten.
That's all it takes, one click and one wrong decision, and the next thing you know, your business name is in the news for all the wrong reasons.
It might sound unlikely, but a North American casino experienced a significant data breach when 10 gigabytes of sensitive data was stolen through a seemingly harmless internet-connected fish tank monitor.