One benefit of a hymnal is the unity that comes from ritual. The Divine Service is full of rituals, and in fact it’s not really possible to have communal worship without rituals. There are the fundamental and foundational rituals instituted by Christ - the preaching of the Word and administration of the Sacraments. The church is created for and built up by those rituals. And there are rituals men have devised over the centuries which, done properly, catechize us, aid in our worship, unite us, and deliver the Gospel to us.
The order we do things in within the service is ritualistic, as well as they way we do them, and these rituals accomplish vastly more than one thing. For instance: making the sign of the cross reminds us that we are saved by Christ’s crucifixion and that we are His. It reminds us of our baptism. It might also serve to refocus our attention. If my mind started wandering, the habit of raising my hand to make the sign of the cross reminds me to pay attention. Seeing others around me reminds me of my neighbor, to whom I’m united and for whom I pray. Young children participate by making the sign of the cross (or really young children by having mom take the hand and make the sign of the cross on them) before they can even understand that much of words.
A hymnal gives a church the blessing of shared rituals.
I am reading the Concordia Commentary on Leviticus by John Kleinig, and he used this great phrase to describe the complexity of purpose and meanings for ritual enactments. He called it a “surplus of significance”. I love it!