Originally Posted by jono1

It could be to do with actually being able to continue a conversation without being interrupted by a signature that's 10x bigger than the actual post. And if you think I'm kidding, I'm not. I was once on a forum where some people's sigs were several paragraphs long and contained dozens of animated gifs and stuff. They eventually had to put signatures inside a div with "overflow: scroll" on them so they would stay small.