this is the problem,if clubs allow large numbers of extremely bad singers,[tone deaf,unable to hold a key],without offering workshops,the singers will not improve,the club will suffer,and the music will suffer,in as much as it will not be an enticement to listeners because the standard is awful.
if I was running a club,I would allow singers providing their instruments were in tune,they could hold a key for the length of a song,that is a pretty low standard,I do not expect amateurs to be as good as professionals.
I prefer if they didnt use word sheets,particularly on guest nights,a goal for new singers to aim towards,to try and work hard to memorise one song for a guest night,its not asking much is it?
if they dont want to do this then they dont sing on a guest night,people pay more money on guest nights,so its not unreasonable to expect a better standard.