Why do they do this?

As it should be. Diesel is easier to refine than gas. There’s numerous reasons that diesel isn’t as popular in the US. One of the first things that comes to mind is climate. In the northern parts of the US, there’s a significant portion of the year that diesel alone will Couple that with the knowledge level of the American public who know nothing about the vehicle that they drive and you wind up with people opting for gasoline powered vehicles. It’s not a big deal anymore because the manufacturers are very proactive in using winter blends mixed with kerosene, but it certainly used to be a significant issue. Then there’s the emissions. The prevailing opinion is that diesel fuel creates far more emissions than gasoline… America is obsessed with eliminating emissions to the point that some states are mandating all new vehicles sold are electric vehicles within the next 12 years or something like that. Of course the technology and infrastructure aren’t there to support that yet, but who knows what will happen in the meantime. The lack of popularity of diesel vehicles means that many stations don’t even sell diesel. I have a diesel truck. There’s five gas stations in my town, and only one sells diesel fuel… when traveling in my truck, I have to legitimately plan out fuel runs and leave a decent reserve of fuel because of the availability of diesel pumps. It’s not so bad where I live because I’m in a super rural area and there’s lots of agricultural uses for diesel, but when I lived in the DFW metroplex, it became quite challenging to find diesel in the city. Industry and transportation still uses a lot of diesel fuel where power is an important deciding factor, but it is becoming less common even there. I am a paramedic, and when I buy a new ambulance now, it’s getting hard to get them with diesel engines. The only way to get an ambulance with a diesel engine in the US is to get one on a truck chassis. A van cutaway chassis doesn’t come with diesel engines anymore. Then when you combine the lower popularity of diesel engines and the lack of availability, it becomes a supply and demand issue making diesel fuel more expensive than gasoline, sometimes significantly more expensive. Anyway, there’s a few reasons why passenger cars in the US don’t use diesel fuel.