Stems from the pre-revolutionary Polizey-state. Know your subjects. Didn't the French (Fouché ?) introduce concierges to look after the citizens?

For the local administration the register of residents is mainly important because German communes get money per inhabitant. Thus there was recently a place in North-Rhine-Westphalia where one did not de-register the local dead. ;-)
At a time when the crime of procuration had been abolished in Germany I recall seeing a Swiss policeman on TV checking the bedding for proof that it had been warmed by two.