We very rarely pay with cash anymore, so we always just add the tip to our card when we pay.
My mother, who worked a second job as a waitress at another breakfast place for many years, never leaves a cash tip on the table. She always hands it directly to the waitress or waiter even if she has to wait around to get their attention again. And if it's a joint tip she'll collect the money and do the same thing with handing it over personally. She wants to make sure the money gets into the right pocket and after years of being on the other side of things, she just doesn't trust people. I'm sure it depends on the area, but things could be pretty sketchy where she worked. I know she also had her arthritis meds stolen out of her locker. How low do you have to be to steal arthritis meds from a middle age lady serving pancakes at 1am?!