Forget the devices -- the risk is to people. If the insulation fails on the power cable and your network cable is insufficiently insulated, then your network cable could end up live. People generally avoid playing with hot power conductors, but no one takes any care to avoid touching network cables or, for that matter, the devices plugged in to network cables.

If they did short I think those tiny diameter wires in the cat6 would pretty much vaporize at household current.

Imagine a short, so Cat6 is now at 120V. Then imagine someone repairing a Cat6 wall jack. Or a kid with a paper clip.

Household current levels don't need to be flowing for it to be dangerous.

Or just someone touching one end of a network cable. The pins on an 8P8C plug are not recessed very far.