The World Cup - let's use a new ball that no-one has kicked before

I know that Adidas had the contract, and it's a commercial decision, but I'm pretty sure that when Ali v Frasier got together they would not have been asked to use a different type of glove.

When Steve Redgrave lowered himself into the boat in the Olympics I'm not sure he'd be enamoured by someone telling him he had to use a different kind of oar.

Why, in the biggest festival of football on earth, are the essential tools of the job subject to last-minute change?