Cuz it's an abomination. Apart from Australians, who are crazy about "contrasts", people with common sense and decency know that some tastes and styles just don't mix together. And so, tainting the delicious pizza or the fabulous pineapple by forcing them together, tastes that clash horribly, you commit a terrible sacrilege which, under a more fair rule, would be punished by at least 10 public lashes.