Even if most rulers and voters were decent ‘responsible’ people then that
would be no substitute for institutions that put a heavy price on personal
irresponsibility. A hereditary monarch too may be a ‘responsible’ person.
Moreover, everybody knows the king, and the typical king expects to remain
in office for the rest of his life and to be succeeded by an heir. Because he is
likely to be blamed for everything that goes wrong, he also has an incentive to
legislate and to make policy for the long term. That is also true for his
entourage of councillors and ministers, who actually are responsible to their
ruler and whom he may hold liable for their deeds (especially if they
jeopardise his prestige, let alone his position).