I know, but I've never seen their ambulances go around any given day, or stumbled upon their ads in the metro, or their sees in the nice quarters of the biggest European cities, which is what makes a historical fossile like the Order of Malta such an interesting sight.
Arilou's point holds a lot of truth, though. Prussia was a peripheral part of the Kingdom of Prussia, which was important largely for being outside the HRE and thus enabling the Prince-Elector to become a king, rather than due to the actual importance of the territory in the polity. Despite the name, the predecessor of the polity known as "Kingdom of Prussia" was Brandenburg, not the Duchy of Prussia.
It's true, I thought Arilou was negating the connection Teutonic Order - Duchy of Prussia, which is what surprised me. While Brandenburg did become the center of the future Prussian kingdom and also of the former Brandenburg-Prussia union, it's the secularisation of Prussia under Grandmaster Albert, a Hohenzollern himself, that made the union, and the kingdom, possible. There's no Kingdom of Prussia without the Knights, but there could have been a kingdom of Prussia without Brandenburg. At least, I see it that way. But it's not my area of expertise, so I accept your judgement.