Is there a reason why there's 3 different "Northern California" sections?
 

NorCal MINIs
Northern California
MidCal Mini

It's redundant and confusing. If I need to search, I have to search three different sections and I'm pretty sure having this many sections also detracts people from posting in it's rightful section (if at all).

Many other forums (with plenty more members and posts) have two Californian sections: NorCal and SoCal.

Is there a reason for this?

There's also Redwood Empire Mini Enthusiasts.

The reason each section is there is to support the clubs that have developed over time. Northern California is the regional fall back section, and when clubs overlap a region often times there is some cross posting. Different clubs have different identities and idiosyncrasies and even levels of activity that change from time to time.