Why are the Sacraments Necessary?

Answer 1

Protestant AnswerThey aren't necessary and they aren't biblical. Roman Catholic AnswerThe seven Sacraments are the signs and instruments by which the Holy Spirit spreads the grace of Christ the head throughout the Church which is his Body. The Church, then, both contains and communicates the invisible grace she signifies. (CCC 774)

Catechism of the Catholic Church: 1129 The Church affirms that for believers the sacraments of the New Covenant are necessary for salvation. (Cf. Council of Trent {1547} Denzinger-Schonmetzer, Enchiridion Symbolorum, definitionum et declarationum de rebus fidei et morum {1965} 1604) "Sacramental grace" is the grace of the Holy Spirit, given by Christ and proper to each sacrament. The Spirit heals and transforms those who receive him by conforming them to the Son of God. the fruit of the sacramental life is that the Spirit of adoption makes the faithful partakers in the divine nature (Cf.2 Pet 1:4) by uniting them in a living union with the only Son, the Savior.

In other words, the sacraments are the normal way that God gives His transforming grace to His people, without which we cannot be saved.