Dear Dmitri,

Thank you for your message. You are quite right; celibacy is not essential to the priesthood. However, it would not be accurate to say it is merely a "disciplinary rule" of the Latin Rite. It is a treasure that was discovered very early on in the Church as particularly suited to the priesthood, so much so that in the Eastern Churches bishops (the fullness of the priesthood) are chosen only from among the celibate clergy, and a priest may not marry after ordination. 

In the Latin Church the vocation to celibate consecration is an integral part of the vocation to the priesthood. How can this be? Because it is God who calls, on his terms, through his representatives. This can be a blow to our pride, because we would prefer to have the vocation on our terms, for us to pick and choose, but that is not the way it is. We cannot change the call; we only have power over answering yes or no to it. 

God bless.