Perhaps I'm so bothered, not by the lack of tip, but by my lack of understanding. I've often wanted to approach this type of guest and ask, genuinely ask, why?
Suddenly your entrance turns into a twilight version of 'Cheers', smiles become frowns, handshakes become accusatory looks and the servers are doing rock, paper, scissors to figure out who gets stuck with you.
The last thing you want is being pegged as a non-tipper, your quality of service will be greatly decreased. And trust me, we peg you, as soon as a regular-non-tipper walks through the door every server who knows alerts every server who doesn't know and we all scowl inwardly.
If anyone out there can enlighten me on the thought process of this type of customer, it would be greatly appreciated.