Singarounds are my favourite and I regularly miss concerts at festivals because |I am enjoying them so much and the quality is so good. Additionally if someone not very good is singing you know it is only going to last a few minutes If the concert you go to see is not good it carries on that way a lot longer.
Sing arounds also provide an arena for songwriters such as myself to test out the reception to new songs. Strangely you do not always know which songs will prove popular and I certainly would not have continued with some of my songs but for the reception they got.