In the US, where race is entirely defined by skin pigmentation and there's heavy segregation ("redlining") of living quarters, sure: databases aren't necessary. But in places where race is defined by heritage or culture, things which can be disguised by the targets of a regime, these databases are a vital part of any serious ethnic cleansing operation. I don't remember the statistic in IBM and the Holocaust that compares Jew survival rates in occupied countries with versus without digitised censuses, but the difference was stark.