See, pirates attacking military units is not profitable in any way shape or form. The fact that it is a bunch of petty criminals versus an armada makes it laughable even.
And no, think about it, if companies see their convoys unprotected, will they send them there?
If Rogues attack liberty, companies like Cryer, Ageira, ect ect would stop trade there all together or would hire much larger escorts.
See, not only you get blown up, but your main source of income is crippled.
In short
By attacking military targets, pirate cripple themselves