Been vegan for 7 years now, haven't eaten meat since I was about 13, so nearly 15 years ago now. It was as simple as realizing that animals in slaughterhouses (and factory farms, which is where most of these animals come from) suffer and it's unfair of me to force that upon them when I have so many other means at my disposal for healthy living. I wouldn't kill a dog or a cat and eat them so I wouldn't kill any other animal, either. Some of the healthiest people on the planet abstain from most or all sources of animal products, such as the Adventist vegetarians/vegans, and some of the most unhealthy people incorporate animal products into their diets, such as Americans. The classic SAD diet. Yikes.
Plus I don't believe in fear mongering tactics. I know people love to say that veganism is inadequate or child abuse, despite that the WHO has declared a balanced plant-based diet sufficient for all stages of life. Typically, people love to read headlines like "vegan child almost dies of malnutrition" without reading that the kid was fed oatmeal and bread with nothing else (in tandem with other child abuse tactics), which has so far been the case with every child abuse claim against vegans (obviously with different foods; I think I read once that a mother (anti-vaxxer no less, poor kid) was feeding the kid soy milk and some kind of single vegetable with nothing else). Interesting, considering there are millions of reported cases of non-vegan parents neglecting their children's nutrition by feeding them chicken nuggets and cookies, but I guess "meat-eating kid nearly dies of malnutrition" is not as good for clickbait. And somehow it's not child abuse to make your kid morbidly obese and let them develop hypertension, type 2 diabetes, and heart disease before puberty. Makes sense.
I guess it's easier to fall for clickbait fake news than it is to actually sit down and look at what happens to innocent and highly intelligent animals. Pigs have been known to be smarter than dogs for a decade now yet people still care more about someone beating a dog than the traditional throat-slitting-style of "slaughter" for pigs. All in all, that's really the biggest deciding factor for me. It's psyducked up what we do to these animals, period. And there are always those who say they "only ever buy" from small farms yet they probably wouldn't buy dog or cat meat from a small farm, regardless of how nicely the dog was treated and then murdered. It's just hypocrisy.
But I'm sure that people reading this would just consider me an arrogant vegan. Funny; I have pretty much no self-esteem and am not in this lifestyle for myself in any way. If I was, maybe I'd care that I'm no longer invited to parties or family get-togethers. :P Last time I went to a party, my mother brought me a vegan-specific meal (because she's an awesome mom like that) and I was heckled for being vegan the rest of the time, despite that I'm quiet and always keep to myself. "I'll just put some deer meat in it"; yeah, real comedian, as if I've never heard "bacon, tho!!"-style jokes before. I hate that the rare times people actually find out I'm vegan, it's like a game of 50 questions follows. Every. Psyduckin. Time. Trust me, people, I ain't doing it for my health, 'cuz ya'll stress me the hell out.