This practice does not interfere with recruitment to the priesthood. Boys can still be altar boys, and if it influences them to become priests, then great. Whether or not there is a girl standing next to a 10 - 14 year old boy (the age of altar servers) during the mass is not going to affect a young man's decision to enter the priesthood when he is 18 - 20. Of course it doesn't. Most of the men entering seminaries today are in the mid-20s, after college, far after the days when they were serving at an altar.
There's other stuff in this "draft" that is far more insidious than restricting the use of altar girls.