I'm kidding, of course, but IIRC pkgsrc (and alikes, such as APT) has a number of limitations, for example a very limited ability to have multiple versions of the same package installed, making it less than optimal replacement.
(I believe a lot of people depend on ability to spin up a new version while the old is running, then do the cutover and shut down the old one after it's not is use.)
Capabilities aside, if you're reproducible and source-based, you're gonna survive binary artifact repository outages a lot better than if you're not.
If there were a comparable culling of the Nixpkgs binary cache, pipelines relying on Nix for their packages would be affected in a much less invasive way: they'd see Nix silently fall back to upstream sources, and reproducibly build from source, wherever the caches binary artifacts became unavailable.
I'm kidding, of course, but IIRC pkgsrc (and alikes, such as APT) has a number of limitations, for example a very limited ability to have multiple versions of the same package installed, making it less than optimal replacement.
(I believe a lot of people depend on ability to spin up a new version while the old is running, then do the cutover and shut down the old one after it's not is use.)