CA's inane open carry law applies to "incorporated" areas, which basically means cities, suburbs, and many small towns. I understand an "unincorporated" area allows loaded open carry. This would be certain wilderness areas, and some small towns, for example.
The history behind unloaded open carry is that in the 60's the Black Panthers were doing peaceful protests while walking around carrying loaded firearms. The populace got scared I guess ( "we can't have uppity colored people doing that!"), and then Gov Reagan ( yes, Ronald Reagan) signed it into law that open carry in incorporated places can only be done unloaded. I've seen the old footage of the Black Panthers, and all they are doing is walking around a courthouse area carrying guns, mostly rifles/shotguns. No rioting, no shots being fired.
So lay the blame on racist over reacting...and Reagan.