They've already demonstrated they can get it in orbit. The fact that they've not done it for this mission was intentional, not a limitation. They wanted the ship back, they didn't want it sitting around in orbit doing nothing being in the way. They don't actually have a mission for it yet, its mission is to prove that it works, so if they put it in orbit then what?

The whole point is that once it's in orbit it has virtually no fuel on board, because that's how they get around the rocket equation, they do fuel transfer on orbit. So in the testing scenario they would have a vehicle with virtually no maneuvering capabilities parked in a stable orbit more or less forever. Eventually its orbit would decay and it would uncontrollably into the Earth, which I think we can all agree is a bad thing.