Until Subaru says otherwise, people are assuming that they're just ducting. Kind of like the pre-2010 Mazdaspeed 3 that didn't have hood scoops (or any other such car that you can think of, I guess).
I like hood scoops because they scream, "I mean business!" It's what makes bro trucks and Honda ricers think twice about trying to do a fly-by on you (twice the thoughtfulness to consider how committed they are to the action they are or aren't about to take upon you).
I like how clean it looks without the hood scoop, which must be what Subaru is going for.