Due to the minimal contact area of the Hubble plugs caused by the need for them to twist when inserted, it's real easy for a small amount of corrosion to cause enough heat to develop to damage it (see photo) and potentially cause a fire. Over the years, I've had to replace 3 shore power cables due to this charing.

The primary benefit of the SmartPlug is that it has something like 20 times the contact area. The other advantage is that it has a much more secure (and waterproof) physical connection, so it is very unlikely to work itself loose as the cable is jostled.