Because you have to devote your attention to blocking him, leaving you no ability to read the course. How they felt a game with rubber-banding that extreme was fit for release in that state shows how desperate Nintendo was to have product on the shelves for Christmas 1997.
Yet more proof of just how overrated Rare was. All of their games had British microcomputer levels of shitty AI, rough design and clearly blockheaded flaws that anyone not as far up their own ass as the Stampers would have fixed before calling a game finished.