Because the community has additional experience and may have thoughts about a proposal. The impression one gets when moderating something can be very different from the impression one gets in the general case. Discussing such issues in advance helps prevent severe unintended consequences from occurring.
In short, you're hoping for the positive part of WWIC, while hoping the negative half doesn't happen.
See references therein for applications to social websites.
Has anyone yet mentioned or reported that for the last couple days, the "karma for last 30 days" is showing zero for everyone? And that we no longer can see the top contributors for the last 30 days either?
Do we have an explanation or estimation for a bugfix on this?