Why do some countries use 110V 60Hz and others use 220V 50Hz for electricity?

[skepticwulf]

I'm wondering why and when this differentiation happened?
Is there any benefits using one to the other?
Wouldn't be safer to use 110V instead of 220V in terms of safety? wouldn't 110V be less harmful to humans compared to 220V when concern is the electric shock?

or is it just like right-driving traffic vs left-driving thing?

 

[Drakkith]

I'm wondering why and when this differentiation happened?
Is there any benefits using one to the other?

See here: http://en.wikipedia.org/wiki/Mains_electricity#Choice_of_voltage

 

[skepticwulf]

Thank you :)