It is rude to not tip for good service.
Matt is out at a restaurant that appears to be slightly out of his budget as he looks through the menu.
Matt wants to save money on his dinner.
Matt orders an inexpensive item off the menu and leaves a modest tip.
Matt enjoys his food, and he does not leave a tip in order to spend less money.
The server is satisfied to get a tip for serving the table.
The server is discouraged as he is dependent on tips to make a living wage.