Much has been said about rational reasons on the desire for monarchy: order, stability, hierarchy, etc. Some even simply find the aestheticism of the monarchy to be endearing, or they desire the tourist revenue from this. However, while God has gifted us with reason, we are not machines, for God has also gifted us with emotion, which serves to drive reason towards goals to be accomplished. For without our emotions, we have no desires and therefore nothing to direct our reason towards. CS Lewis writes that men have a desire for monarchy, and if not sated with a monarch, it will latch itself to wasteful men. I contend that this desire for a monarch is not rational or political, but rather is erotic. What I mean by this is less that it is sexual (though there certainly is an aspect of the sexual) than that it is based on a romantic love. It is not a platonic, or passive love, but is a desirous, possessive, and therefore erotic love that we bear for a monarch. Rather than being shameful or excessive, in this context, erotic love is rendered its most noble, it is the most Christlike expression of love. When Christ loves us, he does so erotically, so the Fathers say, in that he desires to obtain us for salvation. Likewise, when we love God, we desire to possess him, to acquire his grace and love. Likewise, when we love a monarch, it is out of a desire for his rule. This erotic desire for a rightful, lawful king exists even in those who explicitly despise the institution of monarchy. Speak to the most ardent anarchist of Nestor Makhno, and watch his or her eyes glaze over with tears and their voice begin to tremble with admiration, and you will see plainly their desire for him. The people will seek a lawful king even in the absence of a monarchy, and if there are no lawful kings to be found, they will find unlawful, or base monarchs to appease them, and this is what CS Lewis speaks of.
Just as Christ woos or seduces us towards virtue and salvation through his own virtue, a lawful (i.e. virtuous) King seduces our desire for such as himself, for the institution of the monarchy is a miniaturized icon of the marriage of Christ and the Church, of bridegroom and bride. It is, then, an icon of a marriage, for the monarch is not only married to his physical bride, but to his spiritual bride (i.e. the people over which he rules). A lawful king, therefore, is one who rules with an erotic or romantic love towards his "bride", that is, desiring to possess them, and to charm them with his actions, to prove himself worthy of such a fair bride. It is an unlawful king that is neglectful in his love, or who behaves with simple beastly lust, who commits adultery against his bride through pursuing only his own interests at the expense of his bride. Who is flamboyant but without beauty, for beauty is found not only in aesthetics, but in nobility of character. A monarchist is not merely one who believes a monarchy is just, but one who desires a monarch, even if it is a monarch of their heart's desire, and not a living man. Like all people who choose their bridegroom, there is the danger of a poorly made match, of being wedded to an unvirtuous monarch. In such a case, the monarch is unlawful in that his desire for his bride is not genuine, and as such the people maintain their right for a divorce, and to crown a rightful, lawful king. This is not lawlessness, but rather the law of nature, for when adultery is committed, it is a crime not only against the bride, but against God and the covenant, and is a crime which cries out to all humanity to correct by divorce, for erotic immorality was one of the great crimes against which the Law and the Prophets speak against, and which Christ and the Apostles condemn. However, erotic love fulfilled with continence, loyalty, and marriage, is virtuous and a great calling from God. And it is this which is the basis of monarchy. Rather than social contract, it is spiritual contract, for man and wife are anointed by God to follow their love.