How might permanent human life in space begin? I think the old rationales of “if you build it they will come” and “you need fantastically valuable macguffinite or bust” are too simplistic. Mining the platinum group metals is a perfectly decent idea, I think; the PGMs are extremely rare on Earth due to planetary geology, but comparatively plentiful in certain strains of asteroid, meaning we could perhaps not only replace but even vastly expand the supply of PGMs available. Indium, the rarest of all, has something like only a few dozen tonnes of total reserves on the entire planet, iirc.
PGMs and certain rare semimetals also found in asteroids presently are used as industrial chemical catalysts (platinum fuel cells, for example) and are important in the electronics industry as well; see gallium arsenide, and indium-phosphorous transistors, which are useful for packing a lot of processing power into small CPUs. If we had access to more of these metals, it seems reasonable to suspect that many useful new technologies and processes might spin out of it, too.
I think it’s reasonable to suspect that if we go to the asteroids to mine platinum, there will be people working the mines - for maintenance, teleoperation, oversight if not other things. Workers who live in space in the long term, if there arise large enough stations or “towns”, would want to be able to develop their own comprehensive industrial base so as to manufacture necessities ans goods on their own terms, without being tied to the mercy of expensive resupply. Even if humans don’t go, there could still be reason to develop a well rounded, distributed, and redundant larger infrastructure in space to keep the machinery maintained without lots of costly launches from Earth.
(Or, more cynically, the development of broader infrastructure could be expressed through the capitalist drive to externalize flaws in industrial society in the form of mass waste…)
Even before platinum mining, I think it’s reasonable that we could have a spaceborne economy organized around satellite-building and upkeep; smaller-scale plants on near-Earth asteroids could supply at least volatiles for satellite refueling, as well as perhaps less complex, lower grade metals for patching up satellites and stations