Actually, there’s a bit more to it than that, Ken. That’s one of the tougher questions facing the Church. I’m no theologian, but here goes . . .
1. The Church is imitating Christ. Christ only chose men to be apostles, the first bishops, and so the Church is following this example.
2. Realize that the priests represent Christ here on earth. Christ is called the groom, and His Church is His bride. Having a woman priest would be akin to having two brides, which is not marriage as instituted by God.