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.