There is no profit motive in a government run operation. If for example, the local Post Office is taking losses year after year, it doesn't matter because it has a base of tax payers who are forced to financially support its poor business practices. If a citizen doesn't pay their taxes, their property is confiscated. The citizens also risk being fined or imprisoned if they neglect to pay their taxes. People don't like to go to prison, so the Post Office continues to operate like a black hole where reason and logic do not apply.
Here in the USA, we have the (temporary) privilege of being able to print our own currency in any amount needed at any time. If the tax base cannot support their local Post Office, there is always the Federal Government and the printing press available as a last resort to come and bail out the Post Office with currency created out of thin air.