This year the read option is more or less being used as a complement to the major schemes and game plans rather than being the major game plan itself. Even with the number of plays down this year, team's are still having success out of all three pistol formations.
The bulk of the success in 2012 came from a lack of exposure and practice against the scheme. Outside linebackers and defensive ends looked very hesitant in film when seeing the read option for the first time. The secondary players also play the scheme with extremely poor discipline and not knowing where to look as the play develops. In both cases being to aggressive or hesitating for a moment will cause the QB to blow past you or a pitch to the option man.
In 2013 this has changed dramatically. Defensive coordinators are going against the read option with 8-10 guys in the box. They are running blitz' against and creating mismatches on the ends. The players themselves have been staying at home more on the play which causes the QB to make the wrong play or keep the ball himself making him vulnerable to hits.
All in all even with the improved play in all aspects of the defensive front, the read option is still getting its numbers.