Why is vegetarianism generally considered a diet, while veganism is considered a lifestyle?

From what I've learned here, vegans are vegetarians whose views about human-animal relationship involve more than the former eating (or not eating) the latter "Vegetarian" is a simple word description of someone who does not eat meat (including poultry and fish/seafood) and slaughter by products such as gelatin etc. A vegan is a lifestyle that includes vegetarianism PLUS some other principles involving, as I've said, the human-animal relationship. For example, a butcher who kills and processes hundreds of animals a day is still a vegetarian if he/she does not eat any of his own product. A vegan (probably) won't even consider working in a slaughterhouse much less kill the animals her/himself. Personal reasons, moral, health, religion etc, as to why people are vegetarians, are not part of that description.