Or aluminium plus glass, such a brittle combination just for the sake of aesthetics.
Unless you're saying the only point of the iPhone is that people buy it, that isn't sufficient.
Design is very much depending on the intended outcome. Apple wants to sell devices -> design them so that they get bought (make them "shiny", as you put it ;)). Of course this is not the only point of what Apple wants, but it certainly is the biggest one.