For the longest time, PC manufacturers differentiated almost solely on pricing. All PCs were virtually indistinguishable from each other. All the parts that went into their beige cases—including the cases themselves—were commodities. I think this is as good an explanation as any for why these companies can release these kind of knock-off products with a straight face. "Hey, we've always made PCs as indistinguishable from each other as possible. What's the big deal?"
Not to worry, HP. I expect Apple will explain the problem with this approach to you in some detail. In court. Soon.