I have said throughout that my own comments are directed at the UK setup, which I believe was the context of the OP's question.

A group singaround where everyone is joining in the whole song, verses as well as choruses, is a different matter. Then it clearly makes sense for everyone to be singing the same version, which suggests the use of a book or songsheets. If I'm understanding correctly, the concern is not about using these as such, but that one particular book has become dominant to the point where some people feel it is stifling.

In the pubs where the traditional Sheffield Carols are sung they will often provide songbooks, mainly for the benefit of visitors who are not familiar with the carols, many of which are either local or are local variants. I have no problem with this.

It is very different where an individual singer is taking their turn in a singaround or performing a floorspot. No one expects you to come up to professional standards, but that's no excuse for not putting in the necessary work on the songs. Why should the audience be expected to listen to you if you have not?

If you have a medical condition which affects your memory, then clearly that puts a different light on things. However this only affects a minority. Nevertheless, I would encourage the use of discreet cue cards, to support singing from memory as far as possible, rather than singing from a full set of lyrics.

In case anyone thinks I had it easy, my first public performances were at a folk club held at my school. An audience made up of one's 16-18 year old peers (most of whom are there to meet girls rather than out of any interest in folk music) is a far cry from the caring and supportive atmosphere usually found in adult singarounds. I've had my share of forgetting words or making embarrasing mix-ups. I've learned from them - learned to prepare better, and learned tricks to cope with the occasional blanks. You can't learn this if you rely on having the words in front of you.