The large fleet operators do care about this and do go out of their way to improve aero. Look at a UPS 18-wheeler and you'll see trailer skirts, no bug deflectors, window buffeters, etc.
Ironically, the private owner/operators are most often the ones installing accessories to make their trucks look cool and sacrificing immensely for it.
Ironically, the private owner/operators are most often the ones installing accessories to make their trucks look cool and sacrificing immensely for it.