At bar A.
They have karaoke one night a week.
The first week of the month it's on Monday for the lunch crowd.
The second week it's on Satruday for the late crowd.
On the third week it's on Wednesday for the dinner crowd.
On thew forth week it's on Friday it's for the afternoon crowd.
Bar B.
The have karaoke every week on Satudays.
The first week the KJ has 20 singers so it's all karaoke.
The second week the KJ has 15 singers so it's karaoke with DJing.
On the third week the KJ has 10 singers so it's karaoke, Djing and magic tricks.
On the forth week the KJ has 5 singers so it's kitchen sink night complete with Djing, magic and Jay Leno with a splash of karaoke.
Bar C.
They have karaoke every week and they have a different KJ company every week.
On the first week the KJ has a good system but a small selection.
On the second week the KJ sang 5 songs every rotation.
On the third week the KJ had a lousy system but a big song book.
On the forth week the KJ had a decent system and a decent selection but his friends sang 3 songs to your 1.
Bar D.
They have karaoke every week.
On the first week the crowd F Bombed everyone to death.
On the second week the crowd was pretty normal with a few F Bombs.
On the third week the crowd was OK until the KJ played F Bombing hip hop and rap and a fight broke out.
On the forth week the crowd started out normal but the KJ got smashed and the night ended up with the crowd going nuts.
All of the above are real karaoke situations.
If you were the singer which of these nights would you want to got to karaoke?
IMO (don't write me any letters) the karaoke singers have nothing "consistant" to work with or look forward to. The situations are not the best to attract singers on a regular basis.
People in general like consistancy. They like to be in their comfort zone. They don't like change. They want to know what activites they can expect when they go out to spend their hard earned money. If they like karaoke they want to sing and have that expectation.
If your shows aren't attracting all the singers you think you should have...draw your own concusions.
I run a predictable show every night, at every bar. Nobody has to guess if i'll be drunk or sober.
They don't have to guess how the system will sound.
They don't have to guess about the selection.
They don't have to worry about me acting like the star of the show.
They don't have to worry about the fairness of the rotation.
They know if they go to my show on a different night at a different bar, everything will be the same without surprises.
They know whether i have 5 singers or 25 that they will get to sing as much as possible.
They can count on a full night of karaoke music.
They can count on ME.
Bar owners know they can count on me to do a quality karaoke show.
As a karaoke singer of all of the above examples, which show would you want to attend on a regular basis.
Shows that are singer friendly have a better chance of attracting singers.
.....where do you find the time to write so much, and post so often.....I missed you, though, and posting has increased 4 fold since your return.... 
There are 5 of them with many different mini scenarios. They are all open to equal scrutiny.