Okies, let's be pedantic then :P
It's not for mass file trading or trading of illegal files.
As you can see from Khaled's FAQ:
"I'm not happy with the fact that some people use mIRC in a negative way, however mIRC is used by many people, there will always be a some people who use it in ways with which I don't agree."
"Although mIRC has a file-server, it is simple and crude, and was designed years ago for basic personal use, to allow individuals to share files with friends, family, and colleagues, and is nothing like the sophisticated and dedicated file-sharing systems in existence today, which are specifically designed to facilitate the sharing of files on a mass scale."