[vuln]

Commercial diesel engines run for millions of miles / tens of thousands of hours versus passenger or non commercial is measured in hundreds of thousands of miles typically and thousands of hours. Commercials idle for far longer especially in dense areas like cities, rest stops, distribution centers and ports. Maintaining a fleet of diesels can be written off as a business expense (OPEX) while most non commercial use can’t or isn’t. Would be my guess.

[hattmall]

There's also no real competitive force. Gasoline isn't a viable alternative in most cases.