Many churches have moved to using songs projected on the screen, usually meaning selection of songs is restricted to a small number of people. We continue to use a songbook. Why?
1 Corinthians 14:26 says “When you assemble, each one has a psalm, has a teaching, has a revelation, has a tongue, has an interpretation. Let all things be done for edification.” (my emphasis)
Chapter 14 gives principles for when the church meets together. That is the context of verse 26. If each one is to make a contribution including songs (psalms were songs originally) how can they do that if they don’t have access to words? A song book is an easy solution.