For all age groups.
It is the most uncomplicated way to sing songs. In this way we ourselves may become living instruments for God. The whole congregation is choir and praise team at the same time. Everyone is on the same level before God. No one has to remain a spectator.
Under the old covenant God gave specific instructions as to when musicial instruments of what kind were to be used and by who (e.g. Numbers 10, Psalm 150). In the New Testament there is not a single commandment nor an example, according to which Christian churches are to use musicial instruments. Instead we read statements such as these:
"... be full of the Spirit; Joining with one another in holy songs of praise and of the Spirit, using your voice in songs and making melody in your heart to the Lord; Giving praise at all times for all things in the name of our Lord Jesus Christ, to God, even the Father." (Ephesians 5:18-20)
"Let the word of Christ be in you in all wealth of wisdom; teaching and helping one another with songs of praise and holy words, making melody to God with grace in your hearts." (Colossians 3:16)
"Let us then make offerings of praise to God at all times through him, that is to say, the fruit of lips giving witness to his name." (Hebrews 13:15)
These instructions are for the whole congregation - not just for some especially talented members. We all have reason to be thankful. Everyone needs encouragement and teaching. We all want to praise God. It's therefore quite natural to use the one instrument which God has given mankind from the beginning. Using an ever-growing repertoire of older and new songs, our singing is full of variety while at the same time staying tuned to God's word.