Not that I disagree with your sentiment, but you're only able to do this because this class of service providers can't effectively challenge your decision to withhold payment. If the damage is debatable (or pre-existing), the valet isn't going to sue you for his $10 tip.

Compare it to the business world, where if you ship a pallet of widgets and a few of them get damaged, you can't just tell UPS "you broke my shit, I'm not paying you." No, they delivered your shit, however subpar, so they expect payment for the trouble. If you keep withholding based on principle you'll find yourself blacklisted and have your account sent to collections.

The difference, of course, being businesses account for mistakes in their profit margins as a cost of doing business and purchase insurance for large losses. A server is an employee.

And to that: a server is very rarely personally responsible for a bad experience. Restaurant service is a team effort and the service you get merely reflects how well management functions.

A small business usually does not have insurance for this, and the cost of making it right comes out of the owner's pocket.

Also while I can't speak to why other people don't tip, the reasons why I (very occasionally) don't are usually under the server's control. Even if the immediate cause of my unhappiness was not under their control, they had the option of acknowledging the problem and offering an apology. It takes a lot to lose my tip.

If you get bad service, whether it's a rude waiter, cold/incorrect food or something else, the best and fairest course of action is to bring it to the manager's attention. They're usually pretty savvy about the real cause. But tipping a small amount just makes a waiter hate you.