Why not escorts?

Sea too large to stop all pirate attacks

International naval forces will never be able to completely secure the vast area of ocean where Somali pirates are hijacking ships off East Africa, the commander of the EU Naval Force's counter-piracy efforts said Tuesday.

The sea is a big place. And the problems of securing a huge area quite substantial. 

But why no mention of convoys and escorts? Ships seeking to cross a certain dangerous area would join up with others and in the company of a small, fast, fiercely-armed ship crewed by professional soldiers/sailors?

It seems an obvious answer. So is the problem simply one of logistics? Ships travel at different speeds and the convoy must travel at the speed of the slowest vessel. Plus, the formation of a flotilla would require ships wishing to join to sit still in the middle of an ocean while the flotilla was forming up. Since time is money, every hour of delay mid-ocean has a significant cost with days added for the faster (bigger) ships. Is it simply a matter of economics that it is deemed cheaper to take the chance of piracy than to delay by joining a convoy?