The tax break for trucks over 6,000 pounds is a FEDERAL tax break, not just for California. It allows any vehicle used more than 50% for business to be deducted as a business expense in the year purchased, not depreiciated over the usual 5-7 year period.
It was originally designed for trucks (delivery, construction etc.) and was justified as a break for small businesses. A case can be made for the idea, even if you don't support it.
Anyway, as always happens, people came up with a loophole. If SUV's (which as you noted are classified as trucks) could be made larger than 6,000 pounds, and business owners (including lawyers, doctors, etc.) drove them for their businesses (more than 50% of the time, wink, wink), they could get a huge, immediate tax write off.
Therefore, this has morphed into a huge unjustified tax break for the upper middle class and wealthy. Furthermore, it compounds this problem by encouraging the bad energy/environmental policy of building and buying unnecessarily large personal vehicles.
And if you think this is strictly the unintended consequence of a debatably good idea, think again. As part of one of Bush's tax cuts (not sure which one), the maximum dollar amount of this exemption was raised from $25k to $100k. This was well after the rich started exploiting this loophole. Just another tax giveaway to the wealthy, one that was not well publisized.
