Futurists often think that self-replicating machines will change everything. But It's possible to imagine a world where self-replicating technological systems are common, but nobody bothers to use them because they are economically and militarily worthless. In a world with relatively strong property rights and relatively low transportation costs, this could be the expected state of affairs.
The key insight here is that a civilization (meaning a combination of machines, ideas, and people) already is a self-replicating technological system, and every part of that system will always be able to operate more efficiently, through specialization and economies of scale, than anything at the same tech level that must also be small, portable, self-contained, and/or limited to local resources.
It's pretty much a guarantee that no matter what level of technology you have, the output of a portable fabber system is always going to be worse than the output of a factory. Mass production of a single thing by a large facility designed to do that thing will always be more efficient than production from a device that must be small and capable of flexible output. This is true no matter what tech level you have; any tech that makes a fabber work better can also make a factory work better.
For example, in our world, it's easy to see that the output of a printing company is always going to be better, and cheaper per page before delivery costs, then something that you print out of your home printer. Sure, the output of your home printer might be better and cheaper than the output of a printing company in the 1950's. But someone in the 1950's who correctly predicted the capacity of a home printer, and then predicted that nobody would ever buy a printed book or magazine because the home printer could print things on demand more cheaply, would be mistaken. The factory tech also advanced.
It is certainly possible to have a world where all of the components of a replicator can easily come out of a factory, but the output of that replicator (be it useful things or other replicators) would be much more expensive, in terms of resources and time, than the factory version.
It should also be easy to see that any weapon or military system with the design constraint "Must be capable of self-replicating" will be far less cost-efficient than any weapon of a similar tech level that does not have that design constraint. A military power that builds a lot of self-replicating weapons will lose to a power that spends similar amounts of resources on building non-replicating weapons.
People seem to think that resources no longer matter once you have self-replication. But this is not true at all. Any resource that can be consumed by a replicator can also be fed into a factory, and the factory will do a much better job of converting that resource into wealth or power or whatever else you care about.
People also assume that self-replicators will dominate everything because of their capacity for exponential growth. But that implicitly assumes that the adversary is doing nothing with that time. All well-functioning economies grow exponentially whenever they have access to resources, and they do so at a rate based on their productive efficiency. Sure, if you drop a self-replicating weapon in the arctic tundra, then in 100 years you might have billions of drone weapons. But an adversary civilization that spent 100 years converting a similar mass of arctic tundra into weapons using factories will have far more of them (and their weapons will all be 100 years more technologically advanced than yours, and your drone control system is 100 years old and probably easily hacked by modern tech).
On both long and short time scales, factory output dominates. In the short run, they can pump out thousands of things while you are on the first few generations of replication. And in the long run, their increased efficiency and technological advancement will allow them to exponentially increase their productive capacity at a faster rate than your replicators. Your replicators may be doubling every month, but their economy is doubling output every week. You are building things to a more restrictive design constraint, while they can use that tech to crank out specialized factories that efficiently build weapons and factory components.
Of course, all this is before travel costs. If you want to turn an asteroid into a colony, moving the factory to the asteroid is going to be much cheaper than moving the asteroid to Earth and then shooting the factory output back into space. But even in this situation, there is little economic incentive for self-replication. A machine (or system of machines and people) that turns an asteroid into a colony will always have much better performance if it does not also need to be able to create a new colony-creation machine in the process.
So even in the case of a spacefaring civilization with access to self-replication technology, it seems like there's very little economic or military incentive to drop a replicator in an asteroid belt and have it convert the belt into something. No matter what you're trying to accomplish, deploying something built in a large modern efficient factory would always be able to do it better, faster, and cheaper.
The only real motivation for using completely self-replicating systems is independence. If you want to be liberated from the large efficient systems that enable modern civilization, then a self-replicating system loaded with all the important knowledge of civilization can do it for you. But your quality of life, per resources spent, will be far lower than any citizen of that civilization. It will also be significantly lower than anyone who wants to live off the grid but does not insist that their off-grid house and fabber be capable of self-replicating.
Some people will choose to do this, but they will only exist as long as a large civilization actively protects them. They will be utterly incapable of resisting any kind of military aggression, and they are sitting on useful resources. Anything that is capable of sustaining them is also capable of generating wealth for the larger more efficient civilization. So they will never have any real independence in a geopolitical sense, and will always be dependent on a sovereign power for protection.
It will be a performative delusion of independence, probably nestled safely in the territory of a major power while paying property taxes. And this is only possible if the property taxes are a tiny fraction of the economic worth of the resources; if taxes are higher and based on market rates, then the controller of the replicator will never be able to afford them, because the large-scale systems are capable of generating much more wealth from those resources than the smaller systems whose efficiency is constrained by a need to self-replicate.
So in whatever sci-fi setting you like, be it plausible hard sci-fi or something like the worlds of Star Trek or Star Wars, self-replicating systems could be kind of like bitcoin. There's a bunch of random tech geeks that swear it's the next thing, but nobody's ever actually able to find a practical case for it. Occasionally their community makes a useful tech breakthrough, which is immediately absorbed into existing systems and used to make them better.
Some rando could think they're wealthy or powerful because they control a Jupiter-sized mass of mobile self-replicating probes, but traders don't buy anything from them because other people are selling it more cheaply, and any military power's reaction is "Whatever. I could destroy that in an instant but I just don't feel like it right now"
