It must be cultural, but tips, to me, is an American thing. Tipping IMO is for exceptional service. However,and this is not to belittle any, for whom, tips are their primary source of income. I'm trying to understand it. To me, if a tip is part of the cost of going out for the evening, e.g. at a restaurant, then you may just as well incorporate the cost into your food, tat way, at least everyone may derive some benefit from good service. I know that's what it is intended to encourage, but, I wonder if it has become a "right" as opposed to a genuine appreciation for good service. Question: how do you tip the chef who prepared the wonderful meal, yet you never see him, or the laundry maid in the hotel who managed to get that nasty stain out of your wonderful dress? So many other "unsung heroes" who perform the thankless tasks behind the scenes just so you can have a great night out, yet the waitress gets the "credit" for a good night.
What about a notice like: I you want me to keep singing, please ignore the tip jar. If you want me to give up and go home, make it worth my while
. In my case, I'd be rich with a sign like that.