Mostly the complexity and emissions equipment. The emissions components on newer trucks can cost nearly $20,000 if you purchase the replacement parts retail. Until 2003 most of these pickup trucks didn't have any add-on emissions control equipment, it was all done in software to meet the specifications.  

 and in reality, nothing really changed, but a bunch of bureaucrats got paid and a lot of useless junk got made and sold and the consumer is even more in debt because the vehicle has become literally more expensive than it's worth 

 That and they have the power to kick peoples doors in and put them in prison if they "tamper" with them.  

 the system is fucked up beyond all recognition

at some point the pressures of reality will force the matter, for those who aren't already prepared for the collapse