Sure, this is an OK scheme for finding higher quality discussion, but it's just not what the market wants. After the initial adopters had been outnumbered, but

Sure, this is an OK scheme for finding higher quality discussion, but it's just not what the market wants. After the initial adopters had been outnumbered, but long before reddit was popular enough to attract legions of professional marketers, popular subreddits were dominated by puns, memes, highly biased politics, emoting, etc. It's what people upvote, and it doesn't require a reputation system.