Earlier quoted context omitted.
Someone has to go first. If not you, then who? Everything starts with someone going first. And your actions do have an effect: by providing an example to others, making it more likely they too will participate; and economic, by reducing the income generated from the activity.
1/1,000,000,000 has no meaningful impact on any of those. Silent Spring was written by a Rachel Carson and had real impact. However, her personal lifestyle was irrelevant. PS: As to someone going first, that is not an issue when say a state adds a sales tax. In such cases the first person to pay the tax is a sign that it's already in place.
No one said your singular vote (with your wallet) would change everything. But just like voting you help push things in the right direction. And you can, with additional effort, influence more people to vote the same way as you.