Why would they stockpile when they can have any product they want regardless.

The state would act in a socialist society basically to ensure such hording didn't happen. As in, for example, you want a television, you put a request in to the television factory, they send you one. The government would get down your details and register that you have been distributed a television, so you couldn't go and get like more.

But as the society got more communal and less greedy as socialist society got older, eventually the need for a regular state to do such things would decrease until the state 'withers away'.

I suggest you also read my post again in it's entirety, socialism is far more of a individual incentive-modelled society than the current capitalist society. In capitalist society an entire underclass have little to no chance of getting out of such a life, while in socialism you have the full product of their labor.

The argument for socialism is a simple one: Is every individual not entitled to the full product of their labor, to the product of the sweat on their brow?