I can understand the argument for and benefits of diversity of thought, of culture etc. But why passports? It makes as much sense as trying to insist that there must be equal number of right-handed, left-handed, and ambidextrous skilled immigrants.
As of current, that is what the congress prefer. They made the law. Indirectly it was the american public preference because it is the representative of american people.
Yes, that much is obvious. The question, if it was not clear, was an attempt to understand why this is the preference.
Note: This thread is already gone much pedantic IMO, but I give you the benefit of doubt that it is some miscommunication in language. If your point is "it is the way it is, and no explanation is owed to anyone", I will withdraw from the discussion because we don't have much to discuss.