I don't see it as a big deal either, really. It's not like he's obligated to participate, and he's certainly not the first player to forgo the contest. But the media loves creating stories when there really aren't any.
That said... the lad has certainly changed over the past couple of years. He went from being this happy-go-lucky kid who seemed to genuinely love golf to becoming one of the game's biggest corporate players, all-business like.
I think the corporate side of things has jaded his perception a bit. He used to be pretty tight with Westwood and McDowell, but then came the agent issues and management legalities. He felt he was being taken advantage of, I'm sure, and maybe on some level felt that his buddies were in on the gig, trying to cash in on his sudden fame and fortune.
More than anything else - I think those two things really influenced his decision to be more guarded, more business-like. Kinda similar to Tiger - his inner circle doesn't seem too big, and much of the time he seems rather indifferent, as though there's someplace he'd rather be than on the golf course.
Maybe Rory figured out that stardom comes with a lot of stresses, commitments and expectations that initially he never gave much consideration to.
But I still think he's a good kid, and I don't believe he's quite finished winning major championships.