I think it was necroed by a Japanese Twitter addict(@tsutsuii) to display Twitter user icons without X on NetBSD/luna68k, then others started doing all sorts of unholy things with it from w3m with images to terminal-based RDP client.

There aren't a lot of "legitimate" use cases for now, I believe, but it's neat, and IMO an image mode extension for tty kind of makes it whole.