Are there nobles in the Romulan empire? Or emperors? We know there are senators and praetors, etc, but no Lord Vreenak, nor Empress Toreth. Maybe they did away with nobility in the two thousand years since leaving Vulcan or the Vulcans did before the Sundering. These people developed a sophisticated society well beyond our own...I find it difficult to beleive they remain stuck in outmoded forms of governance like clan superiority or divine right. On the other hand, these are Vulcanoids we're talking about
: a people so screwed up they need to supress their emotions to survive.
Man, you know, the Vulcans really are some of the most alien aliens in all Trek.
Maybe the technologically advanced Klingons still use an archane system of governance because they got their technology by reverse-engineering it from their alien opressors, the Hur'q. That may also explain why they haven't advanced that far in the thousand years they've had warp, disruptors, transporters, etc (if the Hur'q had all those...they probably had warp anyway), whereas the Federation has grown in leaps and bounds in a fraciton of that time - because it's a free open meritocracy based on fairness and cooperation.