As an European, I have made the mistake of leaving a tip… and I have been given a tip… and have talked to others who got tipped… and our consensus is that it’s an offensive way of attempted slavery.

If I do a job, I’m doing my job as specified, for the agreed upon price, take it or leave it. I’m not lowering the price to lure a customer, expecting they’ll suddenly appreciate my work so much that maybe they’ll decide to pay me more. If they don’t think I’ll do a good job from the beginning, they can go elsewhere. If for some reason I don’t do a good job, they can have their money back, that’s on me to make sure it doesn’t happen. If I did a good job, and they don’t think so, we can meet in court.