And they were not replicated at the time because this data wasn't considered valuable, and on a larger scale, because there was not a culture of data preservation at NASA.

(It's not clear that they had the ability to replicate this data, anyway -- the reason it was lost was that they needed to reuse the magnetic tapes for data from another project!)

That's why allowing the data to be replicated is so important if you care about preservation. It only takes a few happy mutants who think some otherwise boring data might be interesting and keeping a copy for themselves.

Again, you're assuming that ordinary people had some way to easily "keep a copy for themselves". This was emphatically not the case. This data was not digital. It only existed as a set of magnetic tapes in an unusual format: 1" magnetic tapes containing application-specific analog data. The number of institutions that would have been capable of copying and storing this data would have been small; it's improbable that any individual, "happy mutant" or otherwise, could have done so at the time.

The notion that any sort of data is easy to copy and store is a modern concept. It was usually not the case in the past.