Do you know why are the 13A plug pins designed like these?
Actually, it is a safety design.
When people grip a plug top, slim fingers may accidentally touch the plug pins and causing electric shock. That is why a certified BS 13A Plug has sleeved live and neutral plug pins to prevent this happening.
Meanwhile, a certified 13A plug is designed to have a longer Earth pin. This is a safety feature designed to prevent electrocution in that when a plug top is being inserted an Earth connection is made followed by live pins, or withdrawn from socket outlet Earth connection will be the last to break.
Also, a certified 13A plug allows pins with a 3 degree deflection, which allows the plug top to self-align with the socket apertures during insertion onto a socket outlet.