No one gets a duchy for having the most days in realm. You get the duchy because you have friends, not because your "days in realm" count is higher than anyone else's. Sticking around longer does give you a greater opportunity to be a distinguished member of the realm. And you've had a longer time to make more friends, and to amass more favors that you are owed.
Says you. On Dwilight, I never bothered with the cliques that had formed and imploded over the years. As groups of these ambitious people came and went, I simply went with the flow: aiding the ones in power while their rule was solid, bringing them down when it was obvious they would crumble. Eventually, this led me to have the most days in the realm, as fallen governments exiled themselves (or were exiled).
I never bothered to make myself any form of base of support whatsoever. But with those most days in realm, becoming the duke of Paisly (after rebuilding Paisland myself) and then become both ruler of D'Hara and duke of Paisly required very little on my part, other than a few last-minute deals and campaigning.
Assuming that everyone in power is there because he's at the head of some power-mongering evil clique is just ridiculous. It's quite telling to see what many people think of the BM community on these forums... It would appear that all honest players have gone, and that those who find themselves in positions of power must surely have done something bad for it.
The thing is, when two people present themselves for a position, and you have no prior preference for either and they both offer something similar (or diverge on things you don't really care about), how do you pick which one to vote for? For many people, time in realm is a simple measure of commitment to the realm. "He's been serving here for five years, doesn't he deserve it more than the other guy who's only been here six months and who isn't offering anything more?" It also inspires confidence. After many years, you feel that a certain person is more or less predictable, even if you never really wrote to him. You are more confident in knowing what to expect from him, and for him to continue the culture of your realm since he's been exposed to it longer.