These get are comparatively cheap ways around that.
Otherwise, you do it to make your street car faster (and maybe also pollute more), or worse, just generate a bunch of diesel soot to annoy other people with.
Many states and localities have "visible emissions" rules, where even if your vehicle doesn't have to pass emissions tests, you can still get pulled and cited for actual smoke. I've never been pulled for it (smoke means you're wasting fuel) so I don't know if it's an inconsequential fine or just not enforced generally.
If you spent $100k on a truck, and you could spend $2k more to 'delete' some emissions equipment to prevent $10k+ worth of repairs in the future, would you do it?
At least cars have cabin air filters. I get to suck it straight in unfiltered.
At least cars have smog equipment to reduce the emissions. Motorcycles mostly don't.
I drive a 2013 VW diesel, and this year the warranty covered an EGR and a DPF, which is exactly the kind of thing deletes remove from the vehicle.
That's about $6K in work on a vehicle I paid $14K for a couple of years ago.
Next time, when it is out of warranty, should I take the car to the junk yard? Or delete them and never have another issue? Which is really better for the planet?
Before anybody asks, no I do NOT want to roll coal. It's stupid and obnoxious. You can put a proper tune on a car and not have that issue. Soot is unburnt fuel, which means wasted fuel. You turned it up too high.
Imagine if the warranty was a federal minimum 300k miles/20 years. I bet they would design the components so the labor time is zero to replace them.
When Dieselgate was happening, my understanding is that you were offered a couple of options.
One was to sell back the car. The other was to keep the car, do the fix, and accept an extra 10(?) years of fairly comprehensive warranty. It transferred ownership, which made them fairly attractive as a used car, which is why I have one.
Has saved me literal thousands at this point, but after owning it a couple of years, I understand why everybody was happy to sell them back. They're junk, and the dealership experience leaves something to be desired too.
Some of these warranty claims have had me running back and forth to the dealership. My record is 7 trips before they got it right.
Another dealership left it spraying fuel all over the engine bay. That was a good time.
Edit: people generally don't do things for the "sole purpose of polluting more" it's often functional. Many diesel drivers don't like others who roll coal as the image is bad in general - heavy equipment will often produce black smoke because the engine is being worked for a "function" and it's literally just being given fuel.
I remember turning it off in Europe because trying to start from a dead stop with the engine off in a stick shift is a whole new world of fun I didn’t need.