The purposes of sacraments

Philip Melanchthon lists (he is great at lists) the following purposes of the sacraments:

1. 'they are signs of God's will toward us, or testimonies of promised grace'
2. 'confession' of what we believe
3. 'distinction from other groups'
4. 'so that [God's] name might be celebrated and doctrine spread'
5. 'a reminder of many obligations. First of giving thanks to God, then of mutual kindness of members of the church'

However, as I've already quoted:

although many purposes have been ordained for the sacraments, yet far at the head of all of these must be placed this chief purpose, namely that they might be signs of God's will toward us, that is, added testimonies of the promise of grace

(p. 139, Loci Communes (1543))

This is not an example of the Reformers being unable to escape from Catholicism, but of them listening to Scripture:

Jewish baptism was political and ritualistic, whereas John's baptism was ethical and eschatological (similar to Ps 51:7; Is 1:15-16; 4:4; Jer 2:22; 4:14; Ezek 36:25; Zech 13:1). Gramatically there is an important distinction to be observed. The NT uses active and passive (primarily) forms of bapto and baptizo, while texts referring to Jewish proselyte baptism primarily employ middle or reflexive forms (Oepke, 530-35). Thus what was self-administered in Judaism was seen more as an act of God and surrender to him in early Christianity.

(p. 97, G Beasley-Murray, "Baptism I: Gospels" in IVP Dictionary of the NT)

FYI, Calvin isn't quite as good as Melancthon at clearly ordering the purposes although he is better than most Protestants today:

[a sacrament] is an external sign, by which the Lord seals on our consciences his promises of good-will toward us, in order to sustain the weakness of our faith, and we in our turn testify our piety towards him, both before himself, and before angels as well as men. (Insitutes 4.14.1)