Why are the Plant Lover Trait and Vegetarian Trait not compatible?

I was recently in CAS making a new sim and saw that these traits, Plant Lover and Vegetarian, are considered not compatible. I'm so confused about it; because I would think that a vegetarian could love plants and love taking care of them. I'm just trying to wrap my head around this and I can't think of a logical reason for not being able to have a sim with both of these traits. If anyone has any idea why my game is stating that they're not compatible or know the reasoning for their incompatibility, I'll gladly read your answers.