[mr_toad]

The census predates mass surveillance. The bureaucracy changes slowly.

I doubt the agencies with the surveillance data want to share it.

The data isn’t a count of people. It’s one record per conversation, or whatever. It’s probably riddled with errors and duplicates, incorrect names, dates of birth etc. It probably misses a lot of people (like children). Getting a unique count of individuals, with accurate addresses and demographic information would be a Sisyphean task.