I agree. I coordinate the backing with the front. They are meant to be used, white shows dirt so easily.
More and more lately, I piece some backs to use up what was on the front. I also will make a coordinating block to use for a label and piece it right into the backing.
If there isn't enough leftovers to make the backing big enough, I add coordinating blender pieces from my stash, paying attention to what will end up at the back border edge. I don't want too many seams at the edge and want the binding to look good with the border of the front and the backing.
However, my puzzle-type backs might not please the judges. I'm not making quilts for competition.