**The second and more important reason, Illo said, is that altar service is intrinsically tied to the priesthood and serve as feeder programs for the seminary.**
BTTT!
Inaestimabile donum 18: "There are, of course, various roles that women can perform in the liturgical assembly: these include reading the Word of God and proclaiming the intentions of the Prayer of the Faithful. Women are not, however, permitted to act as altar servers", Pope John Paul II.
Of course, it's a woman's prerogative, and a pope's, to change their mind.