If you were a avid meat enthusiast, you owned your own meat smoker, held barbeques on the weekend, and your license plate said "3atmeat". if you woke up one morning and said, "You know what? Imma be a vegetarian" there is something disingenuous about that. Even if you decide that the treatment of animals by the meat industry is cruel, and you chose to abstain for ethical reasons, if a perfectly cooked and seasoned steak was presented to you, you would probably salivate.

Now, instead, if you found yourself never really enjoying meat, and found that dining without meat was more pleasant to you, then it would seem you were always a vegetarian, or at least have vegetarian leanings. and did not realize it.

EDIT: with respect to the person below: to be clear I am not saying that being gay is necessarily genetic. Perhaps neurological, but my claim is that you cannot fight against what feels natural without some repercussion