Anyone who actually has to use their equipment to get shit done dislikes DPF/regen. It's like Windows Update --- you might be in the middle of a serious task but screech "time for a scheduled update! we dgaf what kind of critical task you were just doing, you want updates!"

Modern diesel systems equipped with DPF tech (which consumes DEF, the fluid) require a regen cycle which is kinda like an oven cleaning itself - they get super hot and burn away particulate before they can be used again. Farmers are more frustrated by the system than the fluid. In fact, DEF is really just piss (urea) which is the same kind of product that they use for fertilizer. Although the prices for urea have skyrocketed recently so perhaps they truly do hate DEF too.

The awesome thing about these 'older' Cummins engines is yes they lack DEF systems and also have mechanical fuel injection. As is commonplace with diesel, there are no spark/glow plugs either. So ostensibly once you have the engine started, it requires zero electricity or computer systems to operate. The RPM of the engine dictates everything else mechanically through gearing. This is a big win for equipment that needs to "just work". Of course they still have sensors and all kinds of systems that are kinda layered on top... but they're not strictly required. This is also why the "runaway diesel" problem exists. You cannot stop an engine like this without starving it of air or fuel.