Might be a public service? I guess many countries already had such a thing with running cost several order higher than such a thing as a TLD, operating for centuries now.
Countries have the loop of "taxpayers pay government -> government funds service -> service benefits taxpayers." You can't do that if you offer the service to the general internet.
Countries have the loop of "taxpayers pay government -> government funds service -> service benefits taxpayers." You can't do that if you offer the service to the general internet.