Why isn't Steemit a Ponzi scheme?

Of course I am asking this question to be proved that Steemit is not a Ponzi scheme. But let me first present why it seems so.

A Ponzi scheme is something that works only as far as it grows, but it cannot reach a maturity with a corresponding equilibrium because stopping growing means crashing.

So let me imagine what will happen when Steemit would conquer the whole planet. Having already all possible users Steemit would be unable to grow more, but still needs to pay a whole world of contributors, so ending inflating its value down to zero and stopping being what it is supposed to be.

Now we are extremely far from this, so it seems something theoretic or not real, but the same it is useful to clarify ideas. In fact Ponzi schemes of all sorts create major imbalances and waste energies and efforts.

So can anybody imagine reaching a situation of equilibrium in which Steemit stopped growing, but the same is able to fulfill all its promises? I hope so, because otherwise Steemit architecture should be rethinked to get a sustainable one, that is one that can work in a state of equilibrium, which is the normal state of nature.

But there is nothing negative in this post, In fact I feel that the aim to empower people of the revenues of their work, creativity and efforts is a very valuable one. But certainly it should be sustainable.
Fran Felisati