[fian]

A bit late to this discussion, but the question of why someone would want to hide information from the government of today is not necessarily the right question.

Governments are not permanent. Significant changes in government can occur through democratic election, revolution, invasion (Ukraine?). Such changes can happen very rapidly. Records can not always be easily purged.

If the incoming government is ideologically opposed to something that you are or you declare (race, religion, political views) and they have a lot of information about you collected by the previous government - then you could very well be in mortal danger.

There are many examples of this in history.

So benign governments should aim to collect the minimum of information required to deliver good service to its citizens. Neither you nor your hopefully benign current government can trust the governments that are to come.