UK and Germany allow citizens of their capital cities to vote, but they still arbitrarily exclude other groups of people living in their countries. One of the scams successfully pulled off by the architects of liberal democratic systems is that it's totally fine and normal to disenfranchise people if they meet certain criteria. As long as it's seen as acceptable to say a non-citizen living within the country's borders cannot vote, for example, the door is open for excluding other groups.