I actually read about this recently:
Fr. Robert Taft, S.J
(who was on the faculty of the Pontifical Oriental Institute)
explains about the history of infant Communion in the Western Church in an article entitled “Liturgy in the Life of the Church” :
“The practice [of communing infants] began to be called into question in the 12th century not because of any argument about the need to have attained the “age of reason” (aetus discretionis) to communicate. Rather, the fear of profanation of the Host if the child could not swallow it led to giving the Precious Blood only. And then the forbidding of the chalice to the laity in the West led automatically to the disappearance of infant Communion, too. This was not the result of any pastoral or theological reasoning. When the Fourth Lateran Council (1215) ordered yearly confession and Communion for those who have reached the “age of reason” (annos discretionis), it was not affirming this age as a requirement for reception of the Eucharist.
“Nevertheless, the notion eventually took hold that Communion could not be received until the age of reason, even though infant Communion in the Latin rite continued in some parts of the West until the 16th century. Though the Fathers of Trent (Session XXI,4) denied the necessity of infant Communion, they refused to agree with those who said it was useless and inefficacious — realizing undoubtedly that the exact same arguments used against infant Communion could also be used against infant baptism, because for over ten centuries in the West, the same theology was used to justify both! For the Byzantine rite, on December 23, 1534, Paul III explicitly confirmed the Italo-Albanian custom of administering Communion to infants…. So the plain facts of history show that for 1200 years the universal practice of the entire Church of East and West was to communicate infants. Hence, to advance doctrinal arguments against infant Communion is to assert that the sacramental teaching and practice of the Roman Church was in error for 1200 years. Infant Communion was not only permitted in the Roman Church, at one time the supreme magisterium taught that it was necessary for salvation. In the Latin Church the practice was not suppressed by any doctrinal or pastoral decision, but simply died out. Only later, in the 13th century, was the ‘age of reason’ theory advanced to support the innovation of baptizing infants without also giving them Communion. So the “age of reason” requirement for Communion is a medieval Western pastoral innovation, not a doctrinal argument. And the true ancient tradition of the whole Catholic Church is to give Communion to infants. Present Latin usage is a medieval innovation.
As we can see from the above there isn’t no good reason not to allow for infant communion within Latin Catholicism, it just isn’t happening now or rather, yet