Why was the California king size mattress invented?

The California king size mattress was invented to provide more space for tall people, who found that traditional king size mattresses were too short for them. (This is true but I've always wondered why they made it narrower? Tall people are not as a rule skinnier). 
This size is also known as a "western king" and it is 4 inches narrower and 4 inches longer than a standard king size mattress. It is 72 inches wide and 84 inches long. (This size is often chosen by couples downsizing to a condo with a smaller master bedroom. The four inches less in width can believe it r not make it easier to fit in furniture pieces)