If I managed to get my grubby hands on a moderately modern computer, I can use all manner of open source software and I can create wonderful new software. The barrier of entry is fairly low in rich countries.
If AMD open sourced all the design aspects of their chips, I would have to get a loan to build 100 million fab to have any practical manner to enjoy it?
I can see that if Intel/AMD/NVidia/Apple shared all aspects fo their chips cross pollination might bring great things, and academic research would be boosted and might end up giving back more to the community at large, but you are talking about very few entities across the world that can afford fabs.