I've always wondered why cooks are so determined to sprinkle it on just about everything they get their hands on. I recently bought a loaf of raisin bread from Panera, figuring that I'd toast slices of it. When I got home with my loaf of bread, I discovered that it had a thick dusting of powdered sugar on the top. What did that add? Absolutely nothing. A little bit of cinnamon sugar -- that I could have understood, but powdered sugar?
If you order French toast at a restaurant, invariably it will arrive at your table with powdered sugar sprinkled over it. Since French toast is meant to be eaten with syrup, the sweetness of powdered sugar is superfluous. Besides, maple syrup has so much more depth of flavor than powdered sugar.
I think the real reason they do it is because they think it makes the dish look more appetizing, but I wish they'd stop. Given the rates of obesity in our country, Americans don't need any more sugar in their diet than they now have.