Understanding Subtlety

  Emily and I just got back from a 25-hour vacation* to Ocean City, Maryland - a family-oriented seashore vacation area. After we finished breakfast, I left our cash tip on the table. Emily asked me to put it under the lip of her dish, which confused me just a tad. After all, the dish would cover maybe one-fifth of the tip (which was paper), so the money would be out in plain sight anyway. Being a thoughtful well-trained husband, I put it under the lip of the dish. When I asked her what good she thought it would do, she said it would be more subtle. That's like much of what NTs do that I have difficulty understanding: If something is going to be obvious one way or the other, what's gained by doing it more "subtlely"? What do you think?