I imagine an important concern is the learning & improvement velocity. Humans get old, tired, etc. GPUs do not. It isn't the case now, but it is fuzzy how fast we could collectively get there. Break out problem domains into modules, off to the silicon dojos until your models exceed human capabilities, and then roll them up. You can pick from OpenGPT plugins, why wouldn't an LLM hypervisor/orchestrator do the same?
https://waitbutwhy.com/2015/01/artificial-intelligence-revol...
https://waitbutwhy.com/2015/01/artificial-intelligence-revol...
They do, though.
Of course, replacing the worn out hardware while keeping the software is easier with GPUs.