> The only explanation is stubbornness: legacy rocketry programs killing innovation to protect their own jobs.

No. It's financial.

Basically... SpaceX only got to where they are because it was literally Elon's money, and Elon's money alone. Like the guy or not (I don't any more), but that was the not-so-secret secret. Elon Musk was willing to risk going from triple-digit millionaire to single-digit millionaire over the Falcon 1, and they would have been out of money, had the third launch not succeeded. Only after that demo flight, the external money actually started rolling in.

In contrast, with the exception of Bezos, all other large scale programs are government/taxpayer funded. That means extreme risk-averseness, an excessive culture of cover-your-ass'ing and no one daring to go too experimental because the blowback from the general public, made rabid by "austerity" and "taxpayer money waste concern groups" for far too long, would instantly kill it (I'm honestly amazed ITER still gets funding). For Europe, the additional complexity is that member states are already whiny bitches when it comes to sending money to Brussels, they want a piece of the pork too, and that kind of crap just doesn't fly (literally) when you need extremely fast iteration times.