Tablet, cellphones. Show me how to produce all of the symbols on a standard keyboard on an iPad, Android tablet, cellphones, etc. without a custom keyboard installed. Now show me how to do it with close to 100% reliability on a virtual keyboard or tiny chicklet keys that aren't your usual device. That's one reason for using common characters only works. Also, see: internationalization- staying with a lowest common denominator saves you from some of the various physical keyboard and charset bastardizations that are floating around.