It's a trend called a "naked cake". One of the ditzy actresses did it a few years back and it's generated a lot of copy cats.
I guess, for some, they see it as a way to save money, and for others, it's a way to save their guests from the evils of too much sugar & fat.
My personal impression is that they look sloppy, unfinished, dry (even if, after sitting out like that for hours, they're not), and unappetizing, but, of course, to each their own. Based on my personal feelings about having my name attached to such a cake, I would decline to do it.