What is annoying is when you attend a club on singers nights (free or not)and then pay to see a guest (not a problem), the same number of singers are also on. This means the guest artist is hardly on at all or else comes back on very late when you are getting ready to leave for home, especially for people who have travelled there by bus or train or, have to get up early next day for work.
It is best if the host just does a couple of songs before the 'artist' comes at the beginning of the night and maybe a nominated 'support' just doing a couple before the artist comes back on after the interval. Weekly clubs have an artist on once a month (or fortnight or as and when), don't singers/musicians have all night to themselves on singers nights?