Why does the British government give more rights to EU citizens instead of British Commonwealth citizens?

Using simple logic, does not the British Empire and Commonwealth have more ties to the UK than all of the other EU countries (excluding the Irish Republic)? Why do EU citizens have more rights than loyal British subjects who had ties to the UK i.e. Canada, Australia, New Zealand, West Indies, etc.? Canada have been a British colony since 1497--should not Canada have more rights to live and work in the UK as an English-speaking British Dominion within the Commonwealth than someone who cannot speak English and lives in Romania? Why do Romanians, Bulgarians, Czechs, etc. have more rights to emigrate to the UK permanently than someone from the Old Commonwealth countries (Canada, Australia, New Zealand, South Africa, West Indies, Rhodesia, etc.)?