The realm of human logic is far, far away from the realm of human basic impulse processing and classification.
What if the 60% of the people thought 21-35 was correct, and the rest thought 51-99 was correct?
This would be peculiar and possibly a coincidence. If people always chose 21-35, it would have to be correlated with a common behavior which I doubt exists. It's very unlikely this will happen and be a consistent result over various sample trials.
Example of human reasoning: "I'm unique, there are not a lot of people like me. So if I pick 21-35%, there will probably not be a majority of people voting this."
People reasoning like this is not unthinkable.
According to you, because humans have consistent behaviour, there would always be one clear winner in elections.
Presidents are usually the tallest of society during their respective period. If you look at top candidates in recent elections, most of them stand over 6 ft.