I think some people need to take a moment to get composed, and to get the tune straight in their heads. They may seem to be fooling with other things, but that's just a cover for getting their composure. This is especially true of a cappella singers. I find if I rush too much to start a song, I often botch the melody and sing something strange for the first verse.
Some say I sing something strange for every verse.
Patience, Jack, patience....
As for books, some of us feel more confident if we have them (even though we may not look at them), and we apologize to those who think us inferior.

-Joe-