Why isn't consecrated virginity a sacrament? In Catholicism, marriage is a sacrament, so why isn't consecrated virginity a sacrament?
Pope Pius XII writes in his 1954 encyclical Sacra Virginitas:


We have recently with sorrow censured the opinion of those who contend that marriage is the only means of assuring the natural development and perfection of the human personality.⁶⁰ For there are those who maintain that the grace of the sacrament, conferred ex opere operato, renders the use of marriage so holy as to be a fitter instrument than virginity for uniting souls with God; for marriage is a sacrament, but not virginity. We denounce this doctrine as a dangerous error. Certainly, the sacrament grants the married couple the grace to accomplish holily the duties of their married state, and it strengthens the bonds of mutual affection that unite them; but the purpose of its institution was not to make the employment of marriage the means, most suitable in itself, for uniting the souls of the husband and wife with God by the bonds of charity.⁶¹


Fr. Hardon, S.J., defines &quot;ex opere operato&quot; as:

A term defined by the Council of Trent to describe how the sacraments confer the grace they signify. Trent condemned the following proposition: &quot;That grace is not conferred 'ex opere operato' by the sacraments of the New Law&quot; (Denzinger 1608). Literally the expression means &quot;from the work performed,&quot; stating that grace is always conferred by a sacrament, in virtue of the rite performed and not as a mere sign that grace has already been given, or that the sacrament stimulates the faith of the recipient and thus occasions the obtaining of grace, or that what determines the grace is the virtue of either the minister or recipient of a sacrament. Provided no obstacle (obex) is placed in the way, every sacrament properly administered confers the grace intended by the sacrament. In a true sense the sacraments are instrumental causes of grace.

And living in consecrated virginity requires grace ex opere operantis (subjective dispositions to receive grace), not grace ex opere operato. This also seems related to why virginity must be freely chosen (Mt. 19:12: &quot;He that can take, let him take it.&quot;) and is not for everyone.