It is also a factor of where our surveys look on the sky. A lot of asteroid surveys have biases to look at the plane of our solar system (since this is where a lot of asteroids are).
It is probably random chance, however there may be some biases from where they come from on the sky (I know people who work on that, but I don't know much about it).
N=3 does not provide very robust statistics yet, give us another decade or two.
Not terribly related but I got curious, the ELT has a reported angular resolution of 0.005 arcseconds. The sad state of public trust has resulted in many people no longer accepting the US landed on the moon at all. Tossing the question of what it would take to resolve the lunar landing sites into a LLM gives a broad requirement of 0.0005 arcseconds. Even still, you could never "prove" it to most people unless it's glass the entire way with no "hoax generating" computers involved.
I can't believe that all those super-intelligent astronomers, who spend hours on their own in the dark, couldn't come up with a better name than 'Extremely Large Telescope'. ;0)
Is this also random chance or is there a reason why it's so close to the plane of the solar system?