It’s as if British people belong to their government.

Legally speaking, British people are subjects, not citizens.

Then somebody needs to let the government know, because the relevant 1981 act is "[a]n Act to make fresh provision about citizenship and nationality". In that 'British subjects' are a quite limited subset of citizens. Most British people are citizens, not subjects.

https://www.legislation.gov.uk/ukpga/1981/61/contents