Git supports two protocols: HTTP and native git (git://). Unfortunately, git over HTTP is terribly slow. As a result, most public repositories don’t prominently display an HTTP URL, because most people would prefer the git:// URL.
In a corporate environment, one does not commonly have the ability to open arbitrary ports on the outside internet. In that case, the git:// protocol is effectively unusable without an unrestricted SOCKS proxy.
To work around the problem, I create my own SOCKS proxy via SSH, then use a wrapper script with git. In essence, this allows me to use git through an SSH tunnel. Any repository, anywhere: one tunnel.