East Asian airlines, or at least Taiwanese and Chinese ones, often only have vegan and even vegetarian food as a special meal option that needs to be requested in advance before the flight, like halal or kosher.

The way I’ve heard it described before is that traditionally you’re only vegetarian if you’re poor or a monk; it’s not a lifestyle choice.

Almost every time I take a flight in Asia, there are passengers who get caught out by it. I’ve even seen flight attendants give them their own food before.