How exactly would one "hoard" money these days? Even if it's just sitting in a bank, that still translates to getting lent out at whatever interest rate that bank charges.

Finite resources (mostly, peoples' time) are expended.

they call that "velocity" of money? it means a rate at which money circulates in some wider way.. it is well-known in some theory circle IMO

So just because it's better than nothing we should consider it good enough?

If all the wealthy would band together to spend their money on convincing every farmer to write software instead, then we'd all starve