From a technical standpoint, it's tough. You've got big expensive machinery that operates at or past any reasonable limits in extreme conditions and moreover ge

From a technical standpoint, it's tough. You've got big expensive machinery that operates at or past any reasonable limits in extreme conditions and moreover gets destroyed with every test if you make the slightest mistake. I know that when I end up with an iteration interval of an hour it seems like development takes forever. SpaceX is able to test, what, every couple months? But the economics is probably more important. The incumbents have such sky-high development costs that reusability seemed like an impossible task to do economically. Last time anyone tried they came up with STS, which was highly capable but ultimately dangerous and ruinously expensive. A new reusable system seemed like it would take half a trillion dollars in development, and would probably never have the flight rate to make it worthwhile. Elon thought that he could do it better. NASA believes designing a reusable system would be too expensive for them. They're probably both right.