Singarounds are a place to share with others the joy of singing - sharing songs together, something that isn't always there at a concert. It is a place where you are more relaxed and can share songs that perhaps you otherwise wouldn't - that does though depend on the type of singaround too! A good MC to keep the continuity going is also important, you dont want a run of fifteen 20 verse ballads with no chorus one after another! If you know your group of singers, you can altenate a chorus song with a ballad to keep the thing flowing well.
For me, who had a transient ischaemic attack a few years ago, my memory sometimes will not now allow me the ability to remember all the words, though I do try, do practise and know the tunes to what I am singing! I more often than not have my words there as a safety net,I am sure there are others like me, but I do agree, if you are going to sing from a sheet, at least try it a few times at home before you inflict it on the general public!
Also running a folk club, as I have for the past year now, I have seen people come just to listen, then flourish into performers...that did mean we had to listen to the bad as well as the good, but the improvement and confidence these people have gained from being allowed to do so is amazing and I'm so glad they had a go!
Finally, I have paid good money to go to concerts in the past to see performers purported to be fantastiuc and been bitterly disappointed. It can go both ways!
Still its all down to taste, you do your thing and Ill do mine, as long as we both enjoy what we are doing, I dont suppose it really matters does it!
Cheers, Lucy