Not tipping at a restaurant where it is customary sends negative signals, which may sometimes have a greater marginal impact than the saved money.

Humans are wired to derive dispositions, including ethical and niceness-related dispositions, from our past behavior. Not tipping sets a bad internal precedent even if no other person you care about signaling to sees you. It sends a bad signal to yourself and runs the risk of making you a worse/meaner/self-serving person compared to what you are/should be.

If this is really about saving money, you should be eating at home, or getting your food someplace cheap that doesn't encourage tipping. Or getting someone else to buy your dinner and having them tip. Or skipping the meal. These things are sufficiently near "don't tip" in the search space that I don't think this post is actually about saving money.