libcurl is part of the macOS API and de-facto standard on any Linux box and commonly available on BSD boxen as well. Microsoft has been shipping curl.exe for a while as well, though not the library.
If Microsoft would also ship the library in %system32%, we would have a truly cross-platform and stable, OS-provided and -patched high-level network protocol client.
If Microsoft would also ship the library in %system32%, we would have a truly cross-platform and stable, OS-provided and -patched high-level network protocol client.
(So that probably won't happen)