You seem fixated on "downloading files over HTTP(S)" and are missing the point.

Nearly every videogame for instance use libcurl as their HTTP stack. You know why? Because it's the best HTTP library for C/C++.

If you have a C/C++ application doing HTTP traffic it's likely using cURL. Or, I dunno, you could look at this page to find out: https://curl.se/docs/companies.html