One of the things that makes the European plugs incompatible is that they ahve different types of earthing. One example is Sweden versus Switzerland. In Sweden, the common socket has earth on the sides of the plug (see http://en.wikipedia.org/wiki/Schuko) whereas in Switzerland the earth is a pin (http://en.wikipedia.org/wiki/AC_power_plugs_and_sockets#Swis...).
By not having an earth, the Europlug fits both the Swiss and Swedish sockets.
One of the things that makes the European plugs incompatible is that they ahve different types of earthing. One example is Sweden versus Switzerland. In Sweden, the common socket has earth on the sides of the plug (see http://en.wikipedia.org/wiki/Schuko) whereas in Switzerland the earth is a pin (http://en.wikipedia.org/wiki/AC_power_plugs_and_sockets#Swis...).
By not having an earth, the Europlug fits both the Swiss and Swedish sockets.