Because it wasn't meant to be a racial term at the time it was created in the first place. It's sort of like Turanism, in a way.
Can someone with Far Eastern ancestry be considered Mexican, Brazilian, Uruguayan, American, Peruvian, and Canadian since these terms are nationalities? So a full-blooded Far East Asian can be called Mexican then? What does vulnerability have anything to do with it? If someone with full Far East Asian ancestry is born in Latin America, and especially if they spent a lot of time there, identify as being Latino, speak Spanish or Portuguese, practice Latin American customs, is Roman Catholic, then why isn't the Latino identity applicable to them? Not that I'm trying to argue with you or anything, but Belize use to be called British Honduras. Many African countries have renamed themselves such as the Democratic Republic of the Congo which was formerly called the Republic of Zaire. In Asia, Myanmar was formerly called Burma. So even nationalities can be renamed despite a nationality being a legal identity. In fact, many legal identities are prone to being renamed as compared to non-legal identities. Legal identities are backed up by law, whereas non-legal identities are backed up by other means such as cultural affiliation, the language they speak, their genetic heritage, the religion they practice, and etc. We tend to think that legal identities are rock solid and permanent, but they're often not. Moreover, why should all identities have to be legally based to be legitimate? Legal identities (such as a nationality) are just one type of identity.