since you asked:

people who stumble through songs they DO NOT KNOW by trying to read them from a book!

There are various levels of ability (mine is only average!), and everyone has to start somewhere and get some practice singing with and for others...and if they DO know the tune, but need a crutch for some words, I can see having a cheat sheet, but I cannot imagine why someone would attempt something that they can't even come close to with the book in front of them!

next on my list is the practice of praising and complementing those who can't sing because "they don't want to hurt feelings"...*sigh*....sorry folks, but there ARE ways to encourage nice people to try harder and help them learn-- it is NOT very useful to applaud them and let them think they did 'OK', when it was truly painful...