Thats actually a good idea. Im thinking that its just low enough that whatever might pass as a breeze there isnt reaching that far to dust off and anything that does blow hard enough carries too much dust of its own. Maybe future rovers should try to include a design that lets it shake its panels and a protocol to shutdown when panels are compromised then reawake n shake at some later time.
I was visualizing the wild shaking of a dog but, to be serious, a series of vibrations might shake a lot of dust off. A little breeze would assist that a lot.