Cost isn’t the only vector. Someone may want to host the runners within a given VPC so they have access to private resources / PrivateLink etc. the job API is a lot narrower of an attack surface area than giving your auth info to GitHub that has enough power to do CI/CD infra changes and such.
There’s also people who use GitHub Enterprise who still need to host a runner fleet, so they could benefit from this too.
There’s also people who use GitHub Enterprise who still need to host a runner fleet, so they could benefit from this too.