Most US & Japanese gear does not have an earth -2 pin (medical gear is different hence they have 3 pin). Looking at those images the earth pin top is free which makes sense. They rely on earth through the negative (blue) (from memory) hence by connecting an earth short circuit.
UK we require "earth grounding" (green & yellow, US/Japan do not.
Many appliances in the USA and elsewhere have two-prong plugs because they are "double insulated."
Double insulated or class 2 electrical appliances are products that have been designed in a way so as not to require a safety connection to electrical earth (These products must NOT have a safety connection to Earth).