It is more due to politics than engineering or logistics. We should have working linear aerospike engines by now. But that project got cancelled(see X-33). We s

It is more due to politics than engineering or logistics. We should have working linear aerospike engines by now. But that project got cancelled(see X-33). We should have had multiple generations of spaceplanes, one half-assed and costly brick did fly, the other was canceled. Many other promising projects met the same fate. We had time, technology and even the logistics in place for incremental development. Instead, 'we' threw a bunch of money down the drain and have nothing to show for it. So we are back to basics, but at least we made a useful leap forward (SpaceX re-usability). Once costs are low enough, new applications will come up, which may become a self-reinforcing cycle. That's what I hope for, at least.