Among other things, safety for minorities. The census is supposed to be secret and never used for any sort of law enforcement, etc. But in our living memory that protection was abused. The US census was used to help round up Americans of Japanese descent and put them in concentration camps in the 40s.

It'd be nice to think that could never happen again. But then you had the Trump people literally trying to put a citizenship question on the census despite every expert saying it was a mistake. The intent was clearly to intimidate (we have this in writing). The question ended up being left off but the damage was already somewhat done.

https://www.nytimes.com/2000/03/17/us/report-says-census-bur... https://www.washingtonpost.com/news/retropolis/wp/2018/04/03...