After the Challenger disaster (1986) it was clear that the Space Shuttle was never going to accomplish its cost and reliability goals. The US military had bet everything on the Shuttle, so it needed a new launch vehicle. The one clear requirement of the new launch vehicle was that it had to be expendable. In fact, the name of the program was "Evolved Expendable Launch Vehicle"[1]

Remember also that when SpaceX started to develop Falcon booster reuse in 2011, every major aerospace company said that reusable vehicles would never make economic sense. Even after the first Falcon 9 recovery and re-flight, most aerospace companies thought reusability was a dead-end and that belief came from the refurbishment cost that Shuttle had to go through.

I count from 1994 (start of EELV) to 2021, when NASA launched astronauts on a reused booster and Peter Beck famously fulfilled his promise to eat his hat if Rocket Lab ever worked on a re-usable launch vehicle.

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[1] https://en.wikipedia.org/wiki/National_Security_Space_Launch