It's because the inference depends on having data from a very large sample of other finds. It wouldn't matter if there were a single Eve and we found her entire skeleton and extracted the DNA perfectly. We couldn't prove it was Eve without all the other samples, and it's beyond unlikely they'll just show up.
I'm disgusted by the convention that findings are controlled by self-interested glory-seeking finders. These belong to the entirety of humanity and should be treated as such, with utmost care and complete openness and humility. We shouldn't tolerate grave robbers any more than bank robbers. Like banks, archeaologists are fiduciaries of the highest order, and should be selected and managed as such, not like salespeople on commission. If you want to seek abandoned treasure, go elsewhere.