Paying taxes doesn't mean working for someone little troll.
You pay taxes to get protection, and other services, and even use votes about somethings in Reverie. Its just like business transaction. That's what World Government counties get for paying taxes, the Marines protects them, they join Reverie etc.
Pirate Island is being protected by the Marines and being a Government country actually would be funny af, so its a fun idea by BB even if he doesn't plan the next step such as taking over the Marijoe next.
Don't mistake BB with someone like Red Dog, who is actually working for Celesital Dragons.