A lot of foodies leave tips in cash for different reasons. Some do it so that their server gets the tip directly without having to worry about the store owner not giving over all the credit card tips. Some do it because of the credit card fees. Some even do it to leave it to the server whether they want to report it as income on their taxes.

But there is a new trend similar to the "illegal tax evasion" scheme that's really just "legal tax avoidance". If you're unclear of the difference, evasion is illegal while the IRS has rules for avoiding taxes legally, like with deductions.