Once, on a date, the girl I was with added some money to the tip I had left (I left somewhere between 15-20%.)
We never dated again.
I think some of these social protocols go both ways. For instance, my wife would never dream of slighting a man by opening her own door without first pausing and giving him the opportunity. Same thing with seating herself. She won't just start ordering at a restaurant, either. And she would consider it completely offensive to offer to pay when we are dining out. (She even "slips" me money if I am short, and they don't take a card.)
But, we were both raised right here... Me in St. Pete, and she, in Largo.
And, the funniest thing about all this is that we both just shake our heads at some women trying to act dumb to puff up the guys they are with. I guess it's just a cultural thing.