I'm sorry Goatfell....but you miss the point. It has NOTHING to do with "better than you" or "not good enough"...it is about people sharing similar tastes or abilities.

If you were a skier, you would ski mostly with folks of similar ideas of where to go and how steep or difficult the course should be. There can, of course, be some overlap, but those who want to zooom downhill at 60MPH may not be inclined to dodge those who are only interested in little gentle slides.

There are two issues involved.....there is **LEARNING** the songs and how the tunes and words go, and there is *PERFORMING** them for or with a group.

The main idea of singing with others is to enjoy the event, I'd think. If you barely know the song and hesitate in the middle or lose the tune and have to glance down at the words every line, then it will not be easy for folks to sing WITH you or to enjoy hearing you.
    If you DO know the song reasonably well, and can manage the tune similarly, then FINE.... you will be welcome most places. Folks who are 'bit' better will be glad to help....but the middle of a session meant for singing the songs is not the best time for learing & practicing the songs.

I will repeat once more my rule: IF you can sing out of a book or from a sheet in such a way that I can't tell with my eyes closed, I will tolerate it! If you almost know the song, but just need a little help to be sure....go ahead! But taking a book and picking a song that you have heard but seldom tried and reading it AT a group seldom works.

I do know that Irish instrumental "sessions" are often even more particular. They often will flatly not tolerate amateur efforts, and will expect you to learn & practice in other ways. I don't pretend to know all the rules.

Ron Olesko says above: "If someone feels more comfortable by using a book, I think it should be encouraged. Having a crutch might be necessary from some people who don't know the songs that well. "
   .....well, it simply depends on where & when and with whom. There ARE groups and places for very informal learning and practice, but there are times when singing from a book if it is not done well (so that someone with eyes closed can't tell) will ruin the mood.

You can preach 'fair' all you want, but it IS the case that if the quality of the music falls below a certain level, some folks will not participate! Others will stay out of sympathy, but suffer. If you know a song you want to hear, but can't lead it well, ASK if someone else will....then sing along and learn it! Get better...practice...take lessons...Most people can eventually manage to participate on a tolerable level.
If singing out of books is the ONLY way you wish to do it, then find a group that does ONLY that.

(I am reminded that square dance groups often have several levels...one for beginners, taught by an experienced dancer...maybe monthly, and then other nights for experienced dancers who do NOT need to be shown all the steps. It interrupts the dance when someone misses a move and the square has to stop and regroup.)

I just don't know what else to say....