I think the main problem in LLM models is that you can not make a PR to an open source project to tweak some training parameters, prove it is an improvement and merge it.

If you can not run the training yourself you can not contribute. So open source contribution model does not work. All examples you gave have a fairly low threshold of capital expenditure required to be a contributor (basically a laptop).

Even back in the 90s a person could get a standard, but powerful, PC to do these things. The one exception was 3d graphics which took quite some time to become affordable and even there it was a single one-time expenditure (a workstation) per contributor.