It's from the US, where "Race" is the official census term for indicating the phenotype of a person. There is a lot of pre existing survey work using the census

It's from the US, where "Race" is the official census term for indicating the phenotype of a person. There is a lot of pre existing survey work using the census categories, so that's why many people keep using them whatever the flaws in the definition might be (and they're probably quite significant flaws).