I think they use them because they make the coaches look elegant when people are shopping. Typically, in your home, people don't ever see your bedroom. In a motor home, it's hard to hide the bedroom when people come over to visit, so it looks nicer if the bed is made.
We like the look of ours. The one in our Monaco was really nice. It was a nice weight and had two flaps sewn in at the top so that your sleeping pillows slid under the flaps and the decorative pillows sat on top. At night, we fold down the comforter and lay it at the foot of the bed. The decorative fit alongside the bed.
We may not be the norm, but we always make our bed. We get up in the morning and make it together so it's not so hard on the back.