The DPF and DEF debate has been raging here since 2014. Do a search and you'll find hundreds of posts on the subject with very few specific Kubota tractor emissions related complaints. I followed these posts with interest when tractor shopping in 2018 and I now own two DPF equipped Kubota tractors.
I've owned a total of 7 Kubotas since 1979, 5 without DPF, and I can honestly say I've noticed NO difference in performance or maintenance with the newer machines. No DPF related issues whatsoever in 4K hours.
Do I wish they didn't have DPF, sure, but it didn't stop me from buying new instead of going for a used tractor that may have someone elses problems.
Keep in mind, these observations are related specifically to Kubota tractors, and may not apply to trucks or other diesel equipped machines.
DPF in itself isn't that complicated.
The problem is when the government gets involved and sets mandates and the industry waits until the last minute to design systems without enough real world testing.
Take automobiles for example. Today gasoline engines barely put anything out the exhaust and the emissions systems are very reliable.
It just took a few decades to perfect.
Diesels are the new challenge, relatively speaking, as the NOx is difficult to remove. It's created in the high pressure/heat of the diesel combustion event.
OTR and larger construction and farming equipment over 74hp require reducing NOx. This brings in EGR and DEF
Fortunately the requirements for diesel equipment from 26-74hp only requires a DPF... Diesel Particulate Filter.
The DPF is just a simple honeycomb filter much like a catalytic convertor in your car. The particulates attach themselves to the walls of all of those "tubes" as they pass across the filter.
There are a few sensors and a fuel injector that are run by computer.
The computer measures input pressure and exhaust pressure to determine level of restriction.
When the restriction reaches a preprogrammed level, the computer commands a regeneration event which is simply spraying some fuel into the DPF which naturally ignites from the high exhaust temperatures, subsequently burning off the partially burnt particulates. They turn into light ash and get blown out the exhaust.
Anyone with electrical controls expertise could design a box that sends the computer those probe readings at the required intervals which would allow you to remove the DPF. But as you just said.. if it's not an issue, why touch it.
Now the big diesels with EGR, DEF and DPF's have been a real problem.
They are known to reduce engine power and engine lifespan. Plus the added complexity of another injection system that squirts urine into the exhaust stream to convert NOx into harmless nitrogen and water vapor exhaust. I can just see the first discovery where an engineer is pissing into the exhaust LOL.
