It's not the fact that he an accomplished NASCAR Driver (obviously) but that he a Championship Caliber driver (IRL Champion, 2006) who is certainly capable of driving a CUP Car. He has a highly successful relationship with Pennzoil, the sponsor of the 22 car (and we all know how important sponsor-driver relationships are, right, Kyle?) who is already under contract with Penske.
It just makes sense on many levels. He may not be Jimmie Johnson yet (or even Kurt Busch) but he's not gonna be Joey Logano either. I would bet that right now Sam could hold his own with David Ragan, Brian Vickers, David Reutimann, Trevor Bayne or Ricky Stenhouse in a CUP Car.
Does that help, Spike?