Actually, there are. Thousands of them. Little known, lesser visited sites of little or no value.

The question should really be, "Why did CR succeed in such a big way, when all other attempts to make such a site, prior to and subsequent to CR, failed"?

I suspect that it might have something to do with social marketing and/or viral marketing, maybe some good SEO, too. Sprinkle in some hard work (more than an afternoon's worth, I'm sure!) and some dumb luck, and there you have it!!!

That's my story, and I'm sticking to it!