Melissa, I think the issue of whether, when, where, and why to use songbooks or songsheets is a topic for another thread (of which there are several). What I think is pertinent to this thread is that a) "worse" musicians maybe need to rely more on chord sheets or lyric sheets than "better" ones do (other things being equal, of course) and b) having your head buried in a book or piece of paper can interfere with watching and listening to the other musicians/singers.   
(Of course, I've known plenty of fiddle players to jam very well with their heads 'buried' in musical scores.)