"Pirate" doesn't mean you have anything in common with other "pirates" except for being on the wrong (right?) side of the law. There's still a fuck-ton of different allegiances, philosophies, "rules" and so on. Hell, I'd say there's even less things in common between pirates than there is between various loyalists, not even taking the rivalries into account.
TLG works very well as a place welcoming outlaws and so on, but gathering pirates under a banner? Ain't happenin'. Not really different from any loyalist RP in that regard.