I’m going to assume you were not raised Western and try to explain. This is to try and be helpful in explaining what might be cultural viewpoints clashing here while trying to be unbiased.

Vegetarian diets are not the norm. So much so that it is safe to not ask someone if they are vegetarian before offering food. A nut allergy is more likely! This is so pervasive that it is unlikely something safe/veg like French fries wasn’t cooked in the same oil as meat. Whether a soup has vegetable broth or a beef broth is easier done by taste than trying to find sources.

In that environment, someone who chooses to deviate from the default is so unusual that being both willing and able to make that change is a strong signal. Being successful here has to be done thoughtfully and is inherently a nonconformist action. A lot of hard choices need to be made like what to about backyard eggs. Which side of ethics is that on?

The jump from there to veganism goes a bit in the opposite direction where it is a membership into an existing group with a set ideology. Eating a backyard egg from a rescued chicken means excommunication. This is less about deviating from default as selecting a new one.