GitHub is popular among developers.
Many developers have faster computers and more computers per household than others that aren't in IT/development.
Many developers, though they pretend to be security minded and focused at times, often have a more lax attitude in practice than system administrators, especially at home or working on personal projects.
Some developers have more usernames/passwords and certs to other servers available than non-developers would.
Some developers have access to other confidential data or newer technology that could be of practical use.