With flaps, they also lower mpg. Not to measurable degree, but they do.
I never had them driving on West Coast. Even I don't look for gravel roads, I happen to land on them from time to time, including about 30 miles gravel road shortcut in BC.
My 2017 Ford had clear film applied behind the wheels, what protected the paint.
At one time in the past I had to accelerate hard with cargo trailer to merge from gravel pull-out area into highway traffic.
The gravel was flying quite high and the cheap diamond plate on trailer show quite some beating, but Ford's bed did not show any chip.