Region locking is the wrong word to use. It is an intentional thing. For example, Blu-rays are designed in one physical and technical specification, but the specification purposefully prevents discs from working worldwide.
Electrical plug and socket designs came about organically as domestic electricity is developing. Economics-wise almost all electrical appliance purchases would be for use in the region where it's purchased so it makes the most sense for them to come with the plug type where it's being sold.
Region locking is the wrong word to use. It is an intentional thing. For example, Blu-rays are designed in one physical and technical specification, but the specification purposefully prevents discs from working worldwide.
Electrical plug and socket designs came about organically as domestic electricity is developing. Economics-wise almost all electrical appliance purchases would be for use in the region where it's purchased so it makes the most sense for them to come with the plug type where it's being sold.