ah, Genie...your reply to me presupposes SO many things!!....."In sing-alongs, having lyrics available enables the entire group to sing a song which otherwise would have been a solo or duet with everyone else listening. When we DON'T use books or lyric sheets in sing-alongs, I often find there's pressure to limit our selections to songs with choruses--which leaves out a lot of great songs."
I can't comprehend why most songs should be sung as a group!...Many songs are done a bit differently by various people, and I have often been in a situation where I had others trying to sing it THEIR way, when it wasn't what I had planned....And some songs are truly best as solos!
I guess I am confused by your use of the term "sing-alongs" ...what I am used to attending are "song circles", called by our group 'open sings'....where there can be MANY types of song, from hymns designed to be sung in harmony, to solos, to call & answer songs, to songs where the POINT is for a chorus.
No matter what you sing, you will "leave out a lot of great songs." I'd far rather just listen to a decent singer do a song they know, rather than try to follow one I DON'T know well. And if the group repertoire is limited to what is on some standard set of 'song sheets' or RUS, frankly, I would be bored stiff!...
Now, if some people WANT to form a group and sing 'from the book', and they all understand that, fine...no law agin' it, but I am just not wired that way...*shrug*....