I've wondered about this too. I once tried to organize a round-robin tournament, and discovered that all the other players preferred single elimination despite its vulnerability to noise and lack of a meaningful second place. In the ensuing argument, I discovered that they do know about problems like this, but they don't care, for two reasons:

1. They don't care much about accuracy. Tournaments ostensibly rank teams by quality, but they're used mostly as ritual contests: the audience wants to know who won, not who would most likely win.
2. They don't like complexity or novelty. They're suspicious of any design they don't understand, because they're afraid it might be gamed, or might have perverse incentives (e.g. where losing a match helps you win the tournament), and because they want everyone, even the dumb jocks, to understand the rules.