Even the Culture isn't completely post-scarcity, though they do a whole lot better with their resources than the Federation. For the Culture, resources are scarce at a very broad scale – but they have Minds which operate at that broad a scale and who engage in something like trade at that scale.
(The real problem that I have with "post-scarcity civilizations" is that no civilization will ever reach a point which can be called post-scarcity. The more stuff you have, the more, bigger, more complicated, more interesting stuff you want, and in particular that's where the stories are. Somebody is always short of something, usually time, and that's where you see your trade economy blossom.)
What you think I mean by post-scarcity and what I mean are slightly different.
What I mean is just any civilization in which any needs that you might have to continue living are so insignificant that everything is provided. I don't think we will ever have a society in which there is no money, but the things we pay for will be vastly different.
The problem with that is that "things that you might need to continue living" is a very flexible scale. Once upon a time, the idea of an abstract connection to a network of computers which talk to each other and allow you to talk to other people wasn't something that anyone would ever think of as "a human need," or even "a human right," but that's what the UN is going for.
Observationally, I think it's safe to say that there will never be a time in which people are going to be satisfied with the life experience that they can possess without engaging with and making use of currency and an economy. Sort of like there will never be a time in which computers have "enough" RAM and CPU – all problems expand to fill all available space.
Human experience expands to fill all available resources – and then some.
To go back to your original post, and making reference of things you've actually said, every crypto token is useful to a society that has replaced physical labor with automation. That's because the value of a token has nothing to do with the amount of physical work that you put in. That's true of the bitcoin, the steem, the litecoin, the cannabiscoin – all of them. It's also true of the US dollar, the euro, the baht, the ruble, and every other fiat currency.
That's what quanta of trade are for, and what they've always been for.
Steem is not "creating the currency by rewarding people who will be the only ones that cannot be replaced by automation" because the majority of the inflationary reward pool is, in fact, going to automated systems, many of which post in order to increase their share of the reward pool. Quite a lot of that money is going to the pockets of those who already have vast piles of that money (see "proof of stake"), who then lease out the power that their pile provides to bots who then lease their votes out to people willing to trade steem for those upvotes and a slightly larger chance of getting some of the reward pool – whose steem goes back into the pockets of the people who are leasing out the SP in the first place to buy more SP.
Rather than being the epitome of society which is run entirely off the sweat of a man's brow, to lift an ironic phrase, the biggest engine in the steem blockchain is, itself, automation.
If you were to drop content creators out of the blockchain altogether, there would still be a good chunk of activity of bots talking to one another trading votes and accruing SP while external investors who are more interested in the cryptocurrency for its lack of fees and rapid transactions Pumping money into it as a value store.
Congratulations, you and I are pretty much completely irrelevant in the grander scheme of things.
I remember when I was young and thought that my existence made a difference. That was many years ago. I've moved past that now.