Nearly every Catholic child receives First Communion, but my understanding is CCD enrollment drops significantly after First Communion. If that is the case, I guess it is a good idea to receive the sacraments together. Many children are deprived of the extra graces available through the sacrament of Confirmation.
Either way, this is another one of those things that I imagine people feel very strongly about one way or the other, but I can see good arguments on both sides.