I believe it has to do with the free-fall nature of the space station. The spinning force likely disrupts the balance we have to keep our station from being pulled further in by gravity, or escaping the clutch of it.
There's likely a better person on here to explain it though. I just think science and space are neat.
Been using it for over 10 years. I have loved the transparency reports, and only wish there were other social and environmental programs we could help with an idea like this. You know, other than freerice.