Why Left hand Handshake

Why do Scouts do a left-hand shake

When Baden-Powell was in Africa, he saw tribal chiefs who carried spears and shields.  He noticed that it was a sign of great trust to offer your left hand when shaking hands.  This was because you had to put down your shield and yet leave the other person with their spear in their hand.

The left hand handshake was adopted by Scouts and is used world-wide.