The attitude of "you have a link, that's good enough" is a silly one. What about file metadata? Who uploaded it? What's their identity in the chat? Because there's no threading in IRC, you can't have a discussion about files/links that persists separate from the channel. Even if you make a HEAD request for every file, what if I want to see the page title of the link or a thumbnail of a linked video or image rather than downloading it?

If we keep the attitude of "IRC solves all the problems it intends to solve," then the number of users whose problems are addressed by IRC shrinks more and more over time.