If they removed 9 of them, I'd be cool. The barriers between them are negligible. You find as much and more diversity in house of human beings.
Fortunately, that's absolutely not going to happen...
While your statement about human diversity is true, "humanity" has a different meaning in the Elder Scrolls universe. Take http://uesp.net/wiki/Lore:Redguard for example: "Redguards do not share the same blood as the other human races, and they have no connection with the ancestral human homeland of Atmora."
Different kind of diversity than that which we see on Earth. While human diversity is cool, exciting, and interesting, it's also much more familiar to us...Part of the exotic allure of the Elder Scrolls universe is the massive variety, and more important than that, the
quality of that variety.
That is, of course, just my opinion.