Christ chose the ordination of priests and bishops be limited to men only. And the Catholic Church has no authority to ordain women to priesthood.  Altar servers are not ordained, thus girls can be altar servers. But there are reasons why altar servers should be limited to boys only :

Boys as altar servers is a good introduction to priesthood. Majority of altar servers do not end up as priests. But this trend can be changed if altar servers are limited to boys only. If girls serve along side with boys, parents and children will not look at altar serving as an introduction to priesthood.

Men and women have different roles in the Church, family and society as stated in the Traditions of the Church and the Scriptures. When boys  serve along side with girls during masses, this contradicts the teachings  of the Church that men and women have different roles in Church, family and society.

The Catholic Church should not adapt the teachings of  the secular society. The secular society teaches that men and women have equal roles in the family and society which is irreconcilable  with the teachings of the Scriptures and the Catholic Church.

The over-use of females in non-ordained roles like lectors, eucharistic ministers, church council members  results in males not seeing religion as a possible vocation, despite the fact that only men can be priests. The use of girls as altar servers furthers undermines the view that men are called by God to be leaders of the Church.