It's our nature to be greed and restless. Restless so we keep getting; greed so that we can have enough. It's why we can survive because we have more than what we need today and spare for tomorrow; The visual of future lead us to agriculture and civilization.
Buddhism believe agony is caused by possession and desire, the real happiness is from the let-go.
We work hard so as to ensure a comfortable future and to cater for all our needs. Work is basically to provide our everyday needs and to keep ourselves occupied. I think it would be kind of weird if we all did not do anything and just sat, it would be a waste of resources and very boring. That could also mean we would be faced with health issues, from not having a healthy diet to obesity, so working hard is really important.