@Markerrag -- I think it is more complex than that. When you leave those roof trusses exposed, you also rule out the possibility of nailing some boards on the bottom and creating an attic. That means less room for storage and people want that.
I don't think it is important to stain or paint a bunch of roof beams so that they are appealing. What you give up is attic space and that limits the appeal of the home.