It's related to the recommended daily servings of each food group. One package of Ramen noodles provides two servings from the grains group. Given that adults are recommended to eat between 6 and 8 servings of grains a day, then yes, one whole package is a reasonable part of a meal.
That alone still wouldn't be a complete meal though. One should add a serving of vegetable or two, a serving or two of fruit, a serving of dairy, 2 oz of lean meat and a serving of fat or oil.
Most people, however, aren't eating ramen as part of a meal, but as their entire meal, and if they are skipping everything else, they may need to eat two or three packages (4-6 servings) simply for the energy required.
tl;dr - serving size isn't meal size.