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It wasnt brought out for that - it was brought out to reduce emissions further after the dpf has done its work. Not all diesels use adblue.

Dpf cleans the emissions as they are leaving the engine ie they trap the unburnt fuel as soot and then when the car regenerates it turns this unburnt fuel into ash which comes out the exhaust which is why they have a lifespan - once they block with ash they are basically useless.

Adblue is usually injected after the dpf system unless the car has a Dpf / Cat combined (the DPF is always first and then the cat second) where it can be injected in to the catalyst but still after the dpf. Adlbue mixes with the exhaust gases specifically Nitrogen oxides (NOX) converting them into harmless Nitrogen and water.

Thats a simple explanation. While the 2 work together to reduce emissions a blocked dpf wont be fixed by filling with adblue.

One of the reason why people think a fill of adblue will unblock a dpf is because if there is a fault with the adblue system at all (low tank / blocked injector etc) it usually wont allow the car to regenerate until that issue is resolved.

Adblue and DPF problems are the bane of my life. Not a day goes by where there is someone with one issue or the other.

The problem is that when the green party urged people to buy diesels you had the little old person buying them and literally only driving to their local shop every day. They never even get a chance to regenerate.

There was one old lady that I remember really well and she had 2 dpfs replaced under warranty plus multiple forced regens.

She used to bring the car into us once a months for us to drive up and down the m50 because she had never driven on a motorway or dual carriage way in her life. The manufacturer wouldnt cover a 3rd dpf because it was down to driving style and she was told she`d need to drive it properly to keep the dpf from getting blocked so she got us to drive it for her.

That was a regular thing with the older generation that bought into the diesel thing.