Genuine curiosity. with the exception of his jail sentence, It seems as thou he fights in May with Shane Mosley and Cotto. After that, he just goes off the radar until next May.
That is simply how the economics of the sport work. Floyd was the highest paid athlete in the world last year for a reason. Fighting once a year serves a few purposes.
In boxing, revenue increases by orders of magnitude as the prominence of fights/fighters increase. Fighters on ESPN typically make ~$50,000 for a main event fight. Fighters on Shobox and BAD typically make $300,000-$500,000 per fight. Fighters on WBC and SBC typically make $1M-$3M. Fighters on PPV typically make $3M-$10M per fight. Floyd and Pac are currently making $30M-$40M per fight.
In order to continue to earn that amount of money, each of those fights needs to be plausibly sold to the public as major events. Fighting once a year creates an artificial scarcity for the product he provides. It becomes an event in and of itself to see him fight because he does it so rarely. The bigger issue than that though is simply the limited number of top level guys he can possibly face. How many of these potential fights would you actually pay for:
http://boxrec.com/ratings.php?sex=m&division=Welterweight
http://boxrec.com/ratings.php?sex=m&division=Light Middleweight
As of right now, maybe Saul Alvarez, Timothy Bradley, and a Cotto rematch? He could potentially fight all three of those guys in one year, but what would he do after that? By spacing out his fights, other fighters can rise in prominence and grow to the point of being potential opponents. No one would have cared about a Cotto fight immediately following his loss to Margarito and yet that went on to be a giant event and a fantastic fight. Who knows who we'll be clamoring for in a year or two.