It was probably a financial decision. Warfarin got well established first and nobody wanted to spend the money to try to crack the market. The people in the US and UK consider warfarin and phenprocoumon so much alike that they don't see much difference.
The Germans and Dutch are the main users of it. It starts to work more rapidly than warfarin and persists longer in the body. It is metabolized by the same enzymes that metabolize warfarin. If your INR gets too high, it is harder to bring the INR down. If it gets too low, it is easier to bring it back up.
The Germans and Dutch think there is some advantage.
I'd be interested as to why you think this drug has an advantage over warfarin.
