Part of the reason for the hush panel is aerodynamics. Remember the big push 20 years ago to get the Cd (aerodynamic drag) coefficient down? One of the problem areas was drag from the undercarriage.
When I changed the fuel filter on my E320 I took notice of the panel that covered it and how it streamlined the undercarriage. These panels are just some of the things that make a Mercedes what it is -- fast, quiet, and fuel efficient.
95 E320 Cabriolet, 131K