That is how most business owners find out their systems have been compromised. Not because money went missing, not because files were encrypted, but because someone who trusted them called to ask what was going on.
The more interesting problem is what the machine holds. Every person who has ever logged into a system from that computer and clicked “remember me” has left a credential sitting in the browser.
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.