I assume you aren’t questioning why there are globally distributed mirrors, but rather why they have to be explicitly listed, as opposed to automatically used.

I assume you aren’t questioning why there are globally distributed mirrors, but rather why they have to be explicitly listed, as opposed to automatically used. I think we can all agree that distributed mirrors are a good idea. They reduce load on undersea cables, can often offer more bandwidth, and have lower latency. But, as for why they are listed... my guess is pretty simple: advertising. These are open source projects that don’t purchase space at these providers, the space is donated. The companies that give them space still need to get something in return. An open source project doesn’t have money, but they can offer eyeballs. So in addition to generally being good citizens, they can also get a little bit of good advertising.