Why Sacraments?
Because we are not [disembodied] spirits but sensuous earthly creatures who can only understand spiritual things when they come to us in humanly perceptible forms, God instituted the sacraments in order that by seeing those signs we might gain a better insight into his benefits, receive a stronger confirmation of his promises, and thus be supported and strengthened in our faith.
Herman Bavinck, Reformed Dogmatics: Holy Spirit, Church, and New Creation, ed. John Bolt, trans. John Vriend, vol. 4 (Grand Rapids, MI: Baker Academic, 2008), 489.