I had a similar thought as OP, except I didnt just "move" the repos and delete on github. Instead, the github mirrors now contain informative readmes with a he

I had a similar thought as OP, except I didnt just "move" the repos and delete on github. Instead, the github mirrors now contain informative readmes with a helpful link to the sourcehut repos. Why? Because unfortunately github is still considered as some sort of industry standard, and this is important for discoverability, voting/favouriting (stars) etc. It also allows someone to star the project on github to show their support.