I totally agree with you, the beauty of P&W is its simplicity, however statistics can never be a bad thing, and it doesn't really add any features to the game,it will only enhance our interpretation of the game.
As a higher percentage of nations reside on the northern hemisphere, during winter times for the northern hemisphere, there is a large dip in supply, while the demand remains roughly the same, therefor it is inevitable that a rise in prices occurs.