When the act was passed the average consumer didn't see pickup trucks as the weird kind of status symbol that they've become today. People used them commerciall

When the act was passed the average consumer didn't see pickup trucks as the weird kind of status symbol that they've become today. People used them commercially- on farms, plowing, hauling, whatever. So presumably in order not to step on the toes of the economy, pickups got a pass and were exempted. Of course, now that these things have blossomed into full-blown vanity displays and are only occasionally used for work purposes, it'd make sense to lump them into the gas-guzzler category. I'm sure the auto manufacturers won't be the ones to suggest it.