Even if I did trust the Government..
Let us assume for a moment that I do trust the government’s motives and intentions. Let us similarly set aside the fact that a future government may be less trustworthy. The past (indeed, current) performance in the creation of large IT projects at a government departmental level (e.g. universal credit) suggests that they could never complete a central government project which would be the largest ever attempted in this country.
So, the best that they would achieve would be a cobbled-together system, that would aggregate multiple databases and datasets – all containing inaccuracies. Would you trust a system, which could decide your entitlement to a pension or to healthcare or even citizenship when the data has been input by a (many?) badly paid, poorly trained and un-motivated civil servant?