You're right that we don't know what new branches of science might be developed that could produce new insights from old artifacts.
But remember the situation. My idea makes it possible to record and analyze ancient finds that currently just disappear. It only gets us 99% of what we want, but in the current system we get 0%.
https://www.logicallyfallacious.com/logicalfallacies/Nirvana...
> currently just disappear
They don't though. The preferences are as other comments have described - to stash the artifacts away in storage or to leave them in the ground for excavation in the future.
Whether or not the laws and common practices are fair to the people who discover the items is a separate matter.
Do you feel that vikings somehow embedded secrets in their coin?
Scrolls have writing on, if we can't yet read them we'd know that there was something else to discover (known unknowns) and clearly wouldn't dispose of them.
Of course the Vikings might have embedded secret extraterrestrial technologies in their coins, but I'd take the bet that they haven't.
The downthread comment about leaving things in the ground is right though -- it was, and is imo, the right thing to do.