Ease of work, lack of imagination and no system is fool proof.
Oldy the senile dwarf is going to vote poorly but he has not been removed from his position due to internal politics - fortunately the clan has a second and a third who if they agree can use magic to compel him to vote a certain way.Even ignoring the dangers of outside hostile parties coming in and meddling with their politics (which we know for a fact can happen, because it did on screen), deliberately enabling ways for you to act dishonorably seems like a bad bet, overall.
It is not dishonourable to do so it is what Oldy would have wanted if they were still in their right mind.
We don't know what circumstances might have brought about the current situation.
We don't know how long they have stood - they might be recent and so the kinks have not been worked out, or they might have worked well for the last thousand years so why change them?And now we can stop ignoring the fact that deliberately putting in those loopholes paves the way for hostile outside parties to come in and subvert your politics. The council would basically have to be idiots for those loopholes to stand.
After the vampire problem they might very well change them to add security.