One main reasons is that the Navy units now changed the way they fight piracy.
Before they were somewhere and reacted to help calls from ships and builded convoys, which btw are not mandatory.
Now they zig-zag close to the Somalian coast and by that prevent the pirates to get out of their hide outs and ports that they can not get to the passing ships anymore.
I am very much afraid that once, the pricay decrease is hailed as "problem solved" by the participating nations, they withdraw their ships and the pirates will be back in the blink of an eye !!
