NASA isn't about space transportation, and the Shuttle wasn't about low-cost reusability.
In government programs, "expensive" and "time-consuming" are virtues, not flaws. The ideal NASA development program is one that lasts decades and pumps billions into Congressional districts. Whether anything useful comes out the other end is almost beside the point.
It isn't easy designing reusable spacecraft, but there's a long technological history to draw on. Including the airline industry, come to that.