This isn't about whether you should tip or how much. Nor is it about Vegas. Nor going out for a business lunch. Recently a woman made a comment about having lunch with a female friend. When she picked up the bill, she was annoyed that the friend wanted to leave the tip. And she made it clear that she dislikes this whenever it happens. Amongst women, it seems that this is quiet common for the non-payer to leave the tip. Do men do this? Or a man and woman as friends out together. Does it make a difference? Just curious if social customs have changed.