How can this go unnoticed when it is common knowledge? There is difference between don't know and don't care. So far the people that care are a tiny vocal minority. Unfortunately.
So they're (probably) not used 'regularly'. That's mildly reassuring. But I have no doubt they're using it as often as they can get away with, which is more than never.
If you have firmware level access to a device like an NIC, you could theoretically circumvent the NIC reporting any network activity at all from your actions. This wouldn't cover external network monitoring of course, but how often do you scour the packet logs of your router's I/O?