Thanks for making that point. A rather important point.
I think the reason why it is old is because it was a bad copy and didn’t get used so much.
The best copies would be used up.
I saw a copy of the Magna Carta in Salisbury. It differed a bit from the official copies, and may have been an early draft, though still on parchment (before the invention of paper). The guy who discovered it was looking for old parchments that he used for coat linings, but thanks to a rigourous education he recognized the Norman French version of the Magna Carta. That is one of 3 contemporary manuscript copies, perhaps thrown away because the scribe left out one line.
Another example of ‘old copies last because they are bad’ trope.