As Salento pointed out, a lot of these categories are to "help" minorities like "Hispanics" and "blacks" take advantage of affirmative action programs. Also, no one is doing dna tests. You self-identify or "claim" certain ancestry. If you write "black" on a college admission form and you look vaguely African admixed when you arrive for your interview, you've got X number of points toward admission. In reality, you're in.
Heck, with American Indians it's even worse. Elizabeth Warren got a leg up with colleges and Executive Boards and professorships because she put "American Indian" on her forms. Turns out that when she got put on the spot by Trump and had to do a dna test, we found out she's probably about 5% "American Indian" and came from a normal middle class family. The colleges and universities don't care: they have a quota to meet, and the government pays the tuition so they're more than happy to go along. Likewise, employers have to meet a certain quota.
"Hispanics" is another minefield. They run the gamut from half Amerindian/half Spanish Mexicans, to Puerto Ricans who run the gamut from minority black and Amerindian to a lot black and Amerindian, to white Cubans with their tiny percentages, to mostly black Cubans and on and on. I don't know whether white Cubans take advantage of it. I don't know, for example, if employers, colleges etc. check family background for wealth, access to good schools etc.
It's just a mess. They should just get rid of affirmative action by "race" or "ethnic" background, and maybe look at "disadvantaged" backgrounds across the Board. I'd want to hire a person who got to college, got good grades, has made a life, who grew up in a dirt poor home in Appalachia going to crap schools.
There's a difference between real life political issues, looking at sociological trends, and genetics tests and analysis.
@Tutkun,
As always you miss the main thrust of the logic and focus on extraneous facts. Let's keep it too tribes if you prefer. When you're a product of five tribes, which one should be chosen? There's the same issue with "whites". Which nationality should an Irish/German/Italian/ put? We have a lot of them. Get it now? They can't really even put European, because as I said Lebanese are "white".
Studies which use these terms are investigating sociological trends. It has nothing to do with genetics, because most people are just self-identifying. To ask someone for a genetic test would be considered a gross invasion of privacy. Also, don't forget: if people don't want to volunteer the information they don't have to.