Apple has just receive a patent for the rectangular design with round corners. It looks like whatever Apple does is done so as to give them a unique identity, which differentiates them from the rest of the companies. This is how apple has apparently gained the sense of prestige and has been able to sell its products to both the rich and the middle-class (even though they are usually overpriced).
The unique characteristics that apple possesses for its devices helps it in associated certain traits to their devices that which can only be found in apple products. This helps in setting it apart.