Then, if the person you're talking to is feeling a bit antagonistic, you'll get jovial-but-annoying questions such as, "but you're wearing leather shoes?", "not even bacon?", "but you need protein to survive?", or - if you're a guy - "but real men eat meat?!"
I should stress that this line of questioning is rarer now than it was when I was a full-vegetarian in the 1990s and 2000s. Perhaps we're so accustomed to people being gluten-, dairy-, and nut-free these days that vegetarianism seems a bit old hat.
As somebody who now doesn't eat sugar (this time for my health), I notice people still try and catch me out. "But there's sugar in that wine?", they'll say. "What about the fructose in those vegetables?"
I used to think I was just oversensitive, until I took to Google and discovered list after list of things that "vegetarians and vegans don't want to hear anymore". Maybe those of us with dietary requirements outside of the norm are a bit sensitive - hence omitting certain foods to we feel more comfortable with ourselves.
But I think there's something more behind this "gotta catch them out" way of thinking. Is it that people are uncomfortable with what diverges from tradition? Do they think we'll push an ideology onto them? Maybe some people just want to feel righteous?
It probably just comes down to fear of the unknown, or the misunderstood. That's part of the human condition: it's easier to close one's mind than to open it.
I'm not really sure why a meat-eater would be afraid of a vegetarian, and want to mitigate their anxiety by somehow proving their herbivorous logic wrong. Equally, I don't understand why people need to raise eyebrows at their sugar-free friends when they drink alcohol, or do the same to lactose-free friends who occasionally give in and partake in a sneaky cheese platter.
My sense is that we, as the human race, love uncovering hypocritical behaviour. That's basically why Twitter exists and why any big company's marketing department is now more focused on fighting fires than putting out flyers. It's our world now: we want to call people out, and any discrepancies we can find are our ammunition.
Personally, I couldn't care less if somebody doesn't want to eat cows but is more than happy to wear them. I know a lot of people don't feel that way - the vegetarian/vegan community itself not exempt. But I have, on occasion, asked a vegetarian what reason they continue to make their choice for, purely out of interest and no ulterior motive.
I think I'm going to stop doing that now. Being questioned is tiresome. People who are asked the same types of things over and over again don't begrudge the individual; it's an accumulative effect. If I can save a herbivore from that irritation for a single day, I might as well.