Eduardo,
It's not so bad if you don't care where the system breaks are. For most hymns, the default behavior does a decent job of producing output with a reasonable density. The issue comes in if you want to lay your music out so that the lyrics are laid out with the same line breaks as if they were poetry without music. The issue is complicated by the narrower format (for the project I'm working on, a 6 inch wide page instead of an 8.5 inch wide page).
This is also not a lyrics-only issue. We talk about bad page turns in sheet music (from the standpoint of being able to physically play the notes and turn the page), but bad line breaks can be as disruptive, especially to those who are not as experienced with a particular piece of music.