1. Homebrew really, really wants you to host your taps on GitHub. The docs are very GitHub-focused: https://docs.brew.sh/How-to-Create-and-Maintain-a-Tap as are downstream projects like dist: https://axodotdev.github.io/cargo-dist/book/installers/homeb...
2. Terraform and OpenTofu public registries support only GitHub, see e.g. https://developer.hashicorp.com/terraform/registry/modules/p... and https://opentofu.org/docs/language/modules/develop/publish/#...
3. Only GitHub allows you to use free minutes on managed Windows and macOS runners, which are essential for building and signing native Windows and macOS/iOS software. GitLab's are in beta and require a paid plan, Buildkite requires you to pay at least $30/user without any bundled macOS minutes and no hosted Windows runners available. And for small shops, keeping the macOS and Windows runners clean is such a stupid time sink, with the small number of minutes involved it's much more preferable to just start with free managed minutes and plan to pay for managed runner minutes later.