What if in the US, if you could prove you were vegan for an entire consecutive year from April 16 to April 15, you had no federal income tax for that year. It gives people an incentive to not kill animals for food (the dairy industry kills baby calves and the egg industry kills chicks).
Anybody wanting to opt out of income taxes like this would have to do the following:
1) Film all the meals they eat for a year and have it sent to a state
2) Send all the receipts of the meals they ordered to the state so the state can fact check and make sure that no animal products were consumed in that year
Assuming that this vetting process happens, the reward is no federal income tax. I don't think too many people will take advantage of this, but those that do would see rewards for helping make the world a better place.
Those that choose to eat animal products won't get penalized for doing so.