It is for the irs, social security, so the community know how many people,children there are to plan for kindergardens, schoolclass size etc. And it also serves as sort of a voters list. But I to not have to go and register to vote or declare myself democrat or republican or independent or what ever. You never have to wonder if you can vote or not.

I used to see it as big brother too, but after what happened during the last two US elections i do not consider it so bad anymore. I mean the US has become a big brother state without any central citizen registration.