I imagine General Mills has done the research, but what if this is the case?

In a riffin' mood.

General Mills Is Serving Wheaties, the Breakfast of Champions, to Younger Consumers. (The New York Times, 6/30/2014)

Maybe is has something to do with milk.  “As we think about trying to reach a younger, more active demographic,” said David Oehler, marketing manager for Wheaties at General Mills, it makes sense to “engage with athletes, and sports, we know this younger demographic are following.”

Related reading: 
Milk consumption drops off massively in the US.  (Global Post, 12/11/2012)

How much?  30% since 1975.

Related posts:
Maybe it's the rainbow colors.  (7/1/2014)

I must be living under a rock.  (7/1/2014)