No money is a bit of hyperbole, but fundamentally, nobody really wants to work hard for the exclusive benefit of everybody else.

Greed is an innate human trait.

Money only works when there is a base level of trust that later, money accepted will have some similar utility.

Because it would be stolen by the government. Ask people in post-Soviet countries about how Soviet governments were stealing money from their bank accounts, from all citizens collectively. No one believed in money under socialism in the USSR. The government could always pull a funny trick called "and now... it's gone". Be happy, comrade, that only your money is gone, you could also be in prison.