they gain control and the concept of redistributing population to areas they need to evolve.
and, yes, they take away the right for people to move from area to area as well, as you will have your internal universal id that binds you to the place of your residence, and no new residence is simply allowed, as it has to be registered by the government. police on the street can demand to see that document, and will deport you if you are not registered.
all the methods are all there.
most common and severe cases were during the war, of course, but it would not be uncommon later as well, in some scenarios.
the gain and goal is of course a limitless control, as it builds up a system where money by itself mean nothing, as money would become only a factor to be able to bribe someone in the government who has decision making powers.
people here in states grossly underestimate what all this purple and green haired scum really wants and really builds. i grew up with that sort of people - they do not want to work and live honest lives, they hate and despise those who earns an honest living by working hard. it is way easier to flip the system to position yourself in society in such a way so you can take away something from those who have it, than to make it yourself. it is all what all this is about, as it was always all the same shit.