They're waiting till everyone stops associating that with Corvette. 

Lights, however, appear to be the most fad driven area of automotive design (except at Lexus). I don't know why manufacturers are so afraid of particularly classic design elements (pun intended) other than that they are afraid of looking old or "dated". Particularly this whole "3D" fad, lately, has gotten out of hand, and produced some of the ugliest lights in the history of automotive design.