It seems that many vegans in the developed world assume the diets of people in developing countries are vegan. While many dishes are indeed vegetable or plant-based, I feel that this belief takes a number of things out of context.
1. The People Mostly Aren't Vegan
While the dishes consist of mostly plant or fungus, the people aren't eating vegetable-based dishes for the sake of veganism. They are eating the dishes, because it's simple to make (from their point of view) and meat is too costly. Animal products are eaten rarely, and when they are consumed, they are consumed in bite-sized or small portions, because it's not cost-effective for one person to eat a gargantuan piece of beef steak. The amount of meat consumed should not be interpreted as vegan, as veganism requires the total elimination of animal products mainly for ethical reasons.
2. The People May Be Malnourished For Scarcity Of Food
People in developing countries are just as malnourished as people in developed countries. While people in developed countries tend to become obese and malnourished due to excessive quantities of junk food, people in developing countries tend to manifest the stereotypical images of malnutrition and poverty. People tend to grab whatever is close, cheap, and convenient. In the United States, that would mean a hamburger, fries, and soda at a fast food restaurant or some candy at the gas station for impoverished people in food deserts.
In Malaysia and other Asian countries, that would mean tofu or rice. In the USA, the junk food provides too many calories and too little vital nutrients. In developing countries, the opposite is true. There is a lot of food rich in nutrients and low in calories, and along with a very physically intensive lifestyle, people become weak and bony, nearing starvation. Vegans may say all they want that "low-calorie" is desirable, but that desirability is only understood within a high-calorie food environment. I don't think they (usually vegans in the developed world) truly understand what it's like to struggle with caloric deficits on an everyday basis. For some first-hand experience to understand these economic and nutritional struggles, I would highly recommend anyone to watch Living on One Dollar (2013). The Economics students in the film actually had to use lard to fatten their meals.
3. The People May Use Bugs As A Source Of Animal Protein
Every time vegans make a health & fitness or food documentary, they always compare meat from livestock animals and colorful fruits and vegetables, as if those things are the only two choices and are polar opposites. It is incorrect to assume that livestock animals have to be some kind of bird, swine, cattle, or fish. In reality, people eat bugs as a source of animal protein. In addition to the inaccurate portrayal of meat, there is much emphasis on what people recognize as "higher animals". Everyone cares about the cute pig that gets slaughtered, and no one cares about the ant that gets stomped or the bee that gets swatted or the mosquito that gets poisoned by natural or artificial pesticide or the termite colony that infests people's homes or the dozens of other critters that become roadkill.
If humans are to respect all animal life, then humans should not use any pesticides (natural or man-made) against the agricultural pests. Humans should not freak out when they see a spider creeping on the wall. Humans should allow mosquitoes to suck their blood and spread bloodborne diseases among the human populations, which can put a check on the exploding human population. Humans should not drive cars, because highways and streets block paths for other animals, many of which have to migrate for food or mates. Unfortunately, humans are doing all those things and making one big mess in the world.
4. The People May Not Have Regular Health Check-Ups
Vegans in the developed world are fortunate enough to get regular health check-ups. If anything goes wrong in their vegan lifestyle, then that can easily be corrected, and the vegan lifestyle can still be maintained. I think vegans should seriously keep in mind that following the vegan diet takes some health risks. These health risks may not be diagnosed in people who eat vegan food all the time but do not have adequate healthcare.
People in developing countries may or may not have adequate healthcare. Maybe the richer ones do, but the poorer ones certainly don't, and it's the poor that eat like vegans. Expecting a life of poverty as the golden ideal for the human race is kind of unrealistic. Maybe it's realistic, if a person has ascetic values. Buddhists are known for such ascetism and ethical living, but they are the exception, not the norm.
5. Developing Countries Are Becoming Richer
Developing countries are becoming richer and richer. As people become wealthier, they want to consume more luxury products, which include meats and sweets and fancy electronics. As a result, global meat consumption rises. Oceans are being overfished; rainforests are being cut down to make way for farmland for big herbivorous livestock animals. The way people obtain food is not sustainable for long, so if people keep on extracting resources like this, there will be a mass starvation. I suppose that is a good thing, because starvation may kill off a sizable chunk of the human population.