[tardedmeme]

It doesn't need to be thousands of developers. Whoever owns the project can use their machine for builds, or spend a few bucks a month on a VPS, or find a sponsor to pay a few bucks for them or provide their own machine (should be easy if the project is any size at all).

My theory is that we waste lots of resources on CI because it's invisible. If you can hear your fans spin up you might try to optimize more, even if the financial cost is still negligible. Back when every developer built the software and ran the tests on their own machine, slow-building projects were the exception not the norm. There was also a much faster feedback cycle for changes to the build and test processes.

Tooling around a self-hosted CI workflow really needs some work to make it as convenient as even the very difficult GitHub Actions.