I cant understand why Triumph doesn't...

I used Dave Quinn too, very good customer service
 
Thing is that in EUROPE - if it is EURO4 compliant - you change and they happen to spot it - BIG FINES. It will also in many countries invalidate the insurance and thus open you to the criminal justice system. Much though I may dislike emissions control - it is the future - learn to accept it on new stuff. I will NEVER buy another modern bike.

I know that most of the major mainstream aftermarket zorst mfrs (esp in italy) are seriously thinking of only making € approved pipes with DIY (not reversible) gutting instructions. The UK is a bit of a grey zone and always has been. But Brexit or not - Euro4 will hit there too. I have a mate here who builds custom bikes. He now has to sell them with a MoT set of parts as well as the fun parts. Some customers are paying him a monthly storage fee for the MoT parts as they don't have space at home.

Added to cost - if small mfrs suddenly got a big contract to (say) supply Triumph or KAWASAKI - from that day on they'd be forced to cut corners reduce costs and specs - so the advantage would go. I see this daily. Sometimes (generally in fact) it's better to say - Nope we'll stay small and independent thank you.

And let's be honest here - Motorcycles in the "exotic" category are VERY expensive. Look at the car you can buy for the price of an R3.