By no means are they necessary. Volvo used to have them then just dropped them completely. Their principal purpose may be to discourage you from working on your own car. I don't know about aerodynamics but the idea that they help with cooling is not just counterintuitive, it's just plain wrong. I have done considering testing on this with two different 124/119s. Take it off - 10 degrees cooler, put it back on, 10 degrees warmer again. MB may have actually been trying to get the cars to run hotter and hence cleaner but it seems to me you want an older used car to run cooler. They also mask fluid leaks which is bad thing.