Pretty much everything you said there is equally applicable to any kind of scarce resource, like oil, steel, or gold. They are all:
- Their yields can not drop to zero by competition (way more demand than supply)
- traded on contracts
- are all scarce
- all "don't produce anything of value" (they can be used as ingredients in production, but are not productions of value in themselves)
- All have the potential stop accumulation of other types of capital when opportunities to invest in these commodities exists
And like money, many of these commodities can last almost for ever, too.
You've mentioned very different commodities. Gold is still money, so you can lend it at interest too.
Oil contains energy, which is not a form of capital but an spendable resource.
I'm not sure is very accurate to say that commodities have yield, but let's concentrate in steel as a form of capital.
For example, when you have a machine made of steel, you could say that is real capital that you will recycle later.
In that case, the reason why its yield cannot drop below the liquidity premium is again because of its competition against money.
If the "yield" you're talking about is the one produced by its changes in price, I would say it's not yield but profit, and drop to zero when an equilibrium is reached.
It doesn't matter that they're traded on contracts and they're scarce because of nature, not because their users have decided so.
They produce things of value when used as capital: a steel made robot arm produces, for example, cars.
They have the potential to stop capital accumulation. But the hoarders think that they will be more valuable in the future, they're putting an incentive on recycling and mining in some sense.
Investors in commodities are providing a service of arbitrage.
Being scarce, natural resources limit us naturally and not artificially.
In a free monetary market, the money users accept the properties of the money, and new moneys can be created to correct their deficiencies. Money can be made of paper and bits without the intervention of a state.
Good for us that they can last forever, that will allow us to mine the dumps in the future.
But is not good for us that most moneys last forever and at the same time are scarce because that's what produces the liquidity premium.