Well,
just take it. This is a already large and still growing community. There may be thousands of reasons why someone would -- a post, anything from bad content to rain outside may count here. The population of this site must have reached a size where it is by far not a trivial quest to understand it's dynamics.

The outcomes of voting are just one sign of this. If you find a way to simulate this, you'll be quite a hero to me...

Regards...

Stefan