And TSTO has some very practical advantages. The mass ratios of the stages are much less constrained, the payload mass is less sensitive to overrunning the mass budget, and most of the mass of the launcher is recovered at much lower speed, making handling entry much easier. The first stage does have to be returned to the launch site but that's not a terribly hard problem.
Are those advantages worth inherently worse amortization costs on the first stage though? A TSTO can have one first stage for ~10ish orbiters since it's only used for 10 minutes while the orbiter has to do all it's supposed to do before coming back into the soup. An SSTO definitionally has to have all parts of the vehicle involved at all stages of operation.
I think a more complicated ground facility is fine if you're doing enough flights.
> Are those advantages worth inherently worse amortization costs on the first stage
If you can launch from and land at any airfield, even if just any military airfield, absolutely. You've opened the market for point-to-point ballistic transport.
The difference is that when a C-17 comes up on radar, there is not a predefined protocol in RU or CN to prepare all of their ICBMs for a rapid response.
What I was getting at, is do all ICBM early warning systems sit on edge more often? That would be my assumption.
We have come close to annihilation from mistakes before, this seems like a path towards more possible mistakes.
Then I guess the answer might include ADB-S and other information-sharing channels. Perhaps only accepting incoming ballistic transports from predefined friendly launch sites. Perhaps only accepting manned ballistic transports.
Ballistic vehicles do not have much cross-range capability, so knowing both where they came from and where they are going is easier than with aircraft. But of course real-time human-seeming communication could be faked with good AI, and even if that were not an option I'm sure some kamakazi pilots would volunteer if necessary. Anything could be faked, but the barriers are not unsubstantial.
This is not me advocating for winged SSTO every day of the week. But I can definitely see the lure.