Most countries do not specify that sockets must be protected by safety shutters, so plug-in covers to go into sockets were developed as a way of keeping fingers and other objects away from dangerous voltages.  Ignorance of the situation in the UK led to UK versions of socket covers being offered for sale.  They are marketed as “Home safety essentials” using such phrases as “essential for keeping curious little fingers away from sockets”, “reduces the risk of children sticking a finger or an object into a wall socket” etc.  Whilst these claims are valid in other countries, they are completely inappropriate in the UK.