Most independant designers won't have a large pool of international resources at their disposal. For example, my company, Ove, is owned by Publicis. Publicis is the 4th largest communications company in the world. They have offices in well over 100 countries and market research from all over the world. They employ anthropologists to do participant observation for products and brand research. Find me an independent designer who has those resources available to them at all times (as we do). I'm not saying that a large firm will do better design (because that's definitely not the case), but there is a reason larger companies go to the larger firms. Large strategic design and branding projects tend to go to the one who has the most resources because that's where companies are made to feel the most comfortable.