Water: Origins On Comets Or Earth?

A recently released analysis of water found on comet 67P/Churyumov-Gerasimenko showed a higher amount of deuterium than is found on our own earths water.Scientists concluded that the theory of comets introducing water to earth is probably not correct.The signature doesn't match.Much money and time has been spent on the Rosetta spacecraft answering that question.It seems to me that a better question would have asked 'Where did the water on comets come from ?" To that question an answer might include since hydrogen is ubiquitous in our universe and so are hot stars it would be a natural result. Maybe scientists are just trying to serialize their work so as to make it last longer.