Wire, plugs, current, safety
I'm a USian with better than average knowledge of the electrical systems here, enough to make me dangerous. My direct experience is with the radial circuits, primarily in the residential electrical. I have also worked with industrial 3-phase delta and wye tapped circuits over 480 volts.
I think a fuse integrated into the plug is proper engineering whenever the wire beyond the plug is rated for less current than the outlet and building circuit. I see the fused plugs here in holiday decorative lights and a few other applications. But, most of the daily use appliances have cords rated for 10 amps or less plugged into 15 amp outlets/circuits, most without a plug fuse. Many of those appliances have a fuse in their power supply, leaving the cord as a weak link.
Keep in mind when talking of fuses or circuit breakers, it is concerning overcurrent protection. There is also GFCI for ground fault protection when the current flowing through the hot is greater than that returning through the neutral and/or ground. The goal of GFCI is to cut the circuit when the current is finding another path besides the neutral or ground since that may be a human providing the circuit path lethally. Then you have the more recent arc-fault circuit protection. It's goal is to break the circuit when a prolonged arcing is occurring. Why? Prolonged arcing causes high temperatures suitable for igniting flammables or melting metals just like arc welding.
This has direct relevance to the "one plug to rule them all". Take USB for example, is has variations for differing power levels through different combinations of volts and amps in the range of 2 to 100 watts. Combine that with backward compatibility either directly or through adapters with older spec cables of lower current capability and no fusing of the wires at the plug and you can see temperatures reaching ignition levels. I know the specs usually cover handshaking to negotiate higher power levels, but various low cost cables and adapters seem to find workarounds to those nasty safety limits. 100 watts may not seem like a lot, but it is more than enough to cause ignition temperatures for a lot of common materials.
Biting the hand that feeds IT
