Because they care more about leaving this planet with less animal cruelty and murder than if they ate meat all their lives. They actually hate that other people are so unsympathetic to the gentle pure lifeforms we share this rock with and just breed them and eat them with no remourse. They are conscious of it and it makes them sick. Unlike most of us they cant unsee the connection from source to product. They have better lives not being forced to be a part of it. What makes it worse is how much bullying and ignorant hopeless comments they get from people close to them and even strangers. Meat is one of the leading causes of deforestation and environmental damage. They hope people will wake up to it one day.