I originally purchased and leased my Prius in Northern California. I realize the gas price is a lot more in Cali, but that cannot be the only factor. The Prius seemed to me to be the most popular car choice around. You saw them like I now see Ford F 150 pick up trucks here in MN. The Prius is just not a huge seller here. Even when I was on vacation in Arizona I saw more there as well.
Where in Minnesota? I certainly see a lot around here, in the burbs of the Twin Cities. And up north really suprirsed me last Fall. There were quite a few of the V models there. I suspect the MPG combined with the extra cargo capacity is quite a draw for running around. I suspect your perspective comes from simply not seeing as many trucks. GM sold 36,584 Silverados and 14,232 Sierras last month, so we aren't exactly a country putting heavy emphasis on reducing pickup sales.
Do not discount tax incentives, car pool lane access or CARB requirements as reasons to buy a Prius in CA.