LLMs actually have tangible use (granted far from bespoke yet). Crypto mining has no tangible benefit.
It seems that much like running a co-op or commune the barrier is whether enough people care to take up the fraction of effort and cost it takes to join such an arrangement.
Even if the social winds did miraculously change, LLMs will never be decentralized for the sole reason that once they're good enough to operate a gun and servo motors every government on the planet is going to lock that shit up fast (assuming massive relentless cyber campaigns somehow don't trigger that response first).