I think many people were/are confused. A few years ago one NASA flight controller made some comparisons. He argued that when a car is relaced by the next version why does it take years to get the new verson on the road when the new version may already have 90% of the older model's characteristics? He made the same comparison with aircraft. He argued that using newer technology means more precision which the aged systems might not be able to accommodate. Therefore, it means starting from scratch with the new tecnology. That is, testing the new technology with unmanned launches first.
Others have argued that the old molds atc. were destroyed to make way for different programs and building new infrastructure.
I am not an engineer or machine designer so I just take their word for it.
Well, whatever the reason they'd better get 'move on' because I read today that the asteroid that had a 3.1% of hitting Earth in 2032 (but now less chance) has a bigger chance of hitting the moon. 🙂