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.