Some of them did even mention it only after a meat eater asked them why they are not eating $X.
As mentioned in my live I met only one vegan that smugly and unprompted talked about veganism. And they were the type who would talk that way about literally every topic.
I am generally careful with stories like that. "Trans bathrooms" is another one of those. My institute has non-gendered bathrooms for the past century, mainly for space reasons. And that never was a problem.
If you love meat, but understand the ethical argument behind not eating it, wouldn't it be practical if vegans were smug assholes that you don't have to listen to? That is why some people want them to fulfill that cliché — I am more interested in the truth, especially the truth that has an impact on my direct life.
¹: There ought to be a number of people everybody met, who are vegans, but you don't know they are, because they did not mention it. E.g. my bands drummer (a old punk) is vegan and it took me two years to figure that one out.